Battery, battery pack, electronic apparatus, electrically driven vehicle, electrical storage device, and power system

ABSTRACT

Provided is a battery in which an area density S (mg/cm 2 ) of a positive electrode active material layer is 27 mg/cm 2  or greater, and a porous film included in a separator has a structure satisfying the following Expressions.
 
0.04≦ Ri ≦−0.07 L −0.09× S +4.99
 
 Ri=τ   2   L/ε′ 
 
ε′=[{( L ×ε/100)− Rz ×0.46/3}/ L ]×100
 
τ={(1.216×ε′ Td ×10 −4 )/ L}   0.5   (Expressions)

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a national stage of International ApplicationNo. PCT/JP2014/004280 filed on Aug. 21, 2014 and claims priority toJapanese Patent Application No. 2013-215006 filed on Oct. 15, 2013, thedisclosure of which is incorporated herein by reference.

BACKGROUND

The present disclosure relates to a battery, a battery pack, anelectronic apparatus, an electrically driven vehicle, an electricalstorage device, and a power system.

Recently, a lot of portable electronic apparatuses have appeared in themarket, and a reduction in size and weight has been attempted. In abattery that is used as a power supply of each of the portableelectronic apparatuses, miniaturization of the battery or effective useof an accommodation space inside the portable electronic apparatus hasbeen demanded so as to realize the reduction in size and weight.

As a battery that satisfies such demand, it is known that a lithium ionsecondary battery having a large energy density is most suitable. As thelithium ion secondary battery, a lithium ion secondary battery using alaminate film as an exterior member has come into practical use whenconsidering, for example, high energy density with small weight, thepossibility of manufacturing the exterior packaging member with a verythin form, and the like.

In the battery using the laminate film as the exterior packaging member,application of an electrolyte solution as an electrolyte and a matrixpolymer compound that retains the electrolyte solution has beenperformed for the sake of liquid leakage resistance and the like, andthis battery has been known as a gel electrolyte battery. PTL 1 to PTL 3disclose technologies relating to a separator that is used in the gelelectrolyte battery.

CITATION LIST Patent Literature

PTL 1: Japanese Patent No. 4075259

PTL 2: Japanese Unexamined Patent Application Publication No.2007-280749

PTL 3: Japanese Unexamined Patent Application Publication No. 2012-48918

SUMMARY Technical Problem

In a battery, it is necessary to suppress deterioration in a capacitydue to repetition of charging and discharging.

Accordingly, an object of the present disclosure is to provide a batterycapable of suppressing deterioration in a capacity due to repetition ofcharging and discharging, and a battery pack, an electronic apparatus,an electrically driven vehicle, an electrical storage device, and apower system which use the battery.

Solution to Problem

To solve the above-described problem, according to an aspect of thepresent disclosure, there is provided a battery including: a positiveelectrode that includes a positive electrode current collector, and apositive electrode active material layer which includes a positiveelectrode active material and is provided on both surfaces of thepositive electrode current collector; a negative electrode; a separatorthat includes at least a porous film; and an electrolyte. The positiveelectrode active material includes a positive electrode materialincluding a lithium cobalt composite oxide which has a layered structureand includes at least lithium and cobalt, an area density S (mg/cm²) ofthe positive electrode active material layer is 27 mg/cm² or greater,and the porous film satisfies the following Expressions.0.04≦Ri≦−0.07L−0.09×S+4.99Ri=τ ² L/ε′ε′=[{(L×ε/100)−Rz×0.46/3}/L]×100τ={(1.216×ε′Td×10⁻⁴)/L} ^(0.5)  (Expressions)

[provided that, Ri: a film resistance (μm), L: a film thickness (μm), τ:a tortuosity factor, T: air permeability (sec/100 cc), d: a pore size(nm), Rz: a surface roughness maximum height (the sum of values of afront surface and a rear surface) (μm), ε: porosity (%), ε′: correctedporosity (%), and S: the area density of the positive electrode activematerial layer (mg/cm²)].

According to other embodiments of the present disclosure, a batterypack, an electronic apparatus, an electrically driven vehicle, anelectrical storage device, and a power system which include theabove-described battery are provided.

Advantageous Effects of Invention

According to the present disclosure, it is possible to suppressdeterioration in capacity due to repetition of charging and dischargingof a battery.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an exploded perspective view illustrating a configuration of alaminate film type nonaqueous electrolyte battery according to a firstembodiment of the present disclosure.

FIG. 2 is a cross-sectional view illustrating a cross-sectionalconfiguration along line I-I in a wound electrode body illustrated inFIG. 1.

FIG. 3A is a schematic cross-sectional view illustrating a configurationexample of a first separator of the present disclosure. FIG. 3B is aschematic cross-sectional view illustrating a configuration example of asecond separator of the present disclosure.

FIG. 4 is an exploded perspective view illustrating a configurationexample of a simple battery pack.

FIG. 5A is a schematic perspective view illustrating the externalappearance of the simple battery pack. FIG. 5B is a schematicperspective view illustrating the external appearance of the simplebattery pack.

FIG. 6 is a block diagram illustrating a configuration example of abattery pack according to a third embodiment of the present disclosure.

FIG. 7 is a schematic view illustrating an example in which the batteryof the present disclosure is applied to an electrical storage system fora house.

FIG. 8 is a schematic view illustrating an example of a configuration ofa hybrid car that employs a series hybrid system to which the presentdisclosure is applied.

FIG. 9 is a graph obtained by plotting measured values of separators inExample 1-1 to Example 1-6, and Comparative Example 1-1 on an L-Ricoordinate plane with an area density (S) of 31.1 mg/cm².

FIG. 10 is a graph obtained by plotting measured values of separators inExample 2-1 to Example 2-11, and Comparative Example 2-1 to ComparativeExample 2-3 on an L-Ri coordinate plane with an area density (S) of 34.3mg/cm².

FIG. 11 is a graph obtained by plotting measured values of separators inExample 3-1 to Example 3-10, and Comparative Example 3-1 to ComparativeExample 3-3 on an L-Ri coordinate plane with an area density (S) of 36.3mg/cm².

FIG. 12 is a graph obtained by plotting measured values of separators inExample 4-1 to Example 4-7, and Comparative Example 4-1 and ComparativeExample 4-2 on an L-Ri coordinate plane with an area density (S) of 38.5mg/cm².

FIG. 13 is a graph obtained by plotting measured values of separators inExample 5-1 and Comparative Example 5-1 on an L-Ri coordinate plane withan area density (S) of 42.0 mg/cm².

DETAILED DESCRIPTION Technical Background

First, the technical background of the present disclosure will bedescribed for easy understanding of the present disclosure. PTL 1(Japanese Patent No. 4075259) described in [Background Art] discloses abattery in which a separator having a film thickness of 5 μm to 16 μmand a porosity of 25% to 60% is used, and which includes a Co-basedpositive electrode including lithium cobaltate and the like, and a gelelectrolyte.

However, in the battery disclosed in PTL 1, the relationship between thearea density of a positive electrode active material layer and thethickness of the separator is not considered. Therefore, for example, ina case where the area density of the positive electrode active materiallayer is set to 27 mg/cm² or greater, the electrode length decreases andthus the amount of active material may decrease in comparison to thecase of using a separator of the present disclosure in a battery havingthe same size, and thus the energy density of the battery decreases.

In addition, in this case, when using a separator outside of the rangein the present disclosure, it is difficult to mitigate an over-voltagethat is caused by a current density that increases due to the areadensity of the positive electrode active material layer, and thus thecycle lifespan is apt to decrease due to a decomposition reaction of anelectrolyte solution.

PTL 2 (Japanese Unexamined Patent Application Publication No.2007-280749) discloses a technology capable of providing a batteryexcellent in cycle characteristics by using a separator having airpermeability of 80 sec/100 cc to 300 sec/100 cc.

However, in the case of applying the technology disclosed in PTL 2 to aseparator having a large film thickness, ion permeability of theseparator decreases, and thus a local over-voltage on an electrodesurface tends to increase during charging and discharging. Particularly,in a case where the area density of an electrode increases beyond anarbitrary range, clogging of the separator occurs due to electrolytesolution decomposition due to the over-voltage, and as a result, thecycle characteristics deteriorate.

PTL 3 (Japanese Unexamined Patent Application Publication No.2012-48918) discloses a configuration capable of providing a batteryexcellent in cycle characteristics in the case of using a separator inwhich the film thickness is 5 μm to 25 μm, and the number of pores perunit area in the separator is 200 or greater.

However, in the battery disclosed in PTL 3, in the case where the areadensity of the positive electrode active material layer is equal to orgreater than an arbitrary constant range (for example, 27 mg/cm² orgreater), there are ranges of the air permeability and the porosity ofthe separator at which clogging of the separator due to the over-voltageis promoted. Therefore, in the case of using the separator, in which theair permeability and the porosity are in the ranges, in a battery inwhich the area density of the positive electrode active material layeris equal to or greater than an arbitrary constant range, the cyclecharacteristics deteriorate.

Accordingly, the present inventors have obtained the following findingafter a thorough examination. In a case where the area density of thepositive electrode active material layer is set to 27 mg/cm² or greater,when using a separator having a predetermined structure, the followingeffect can be obtained.

It is possible to increase the amount of an active material per the samevolume, and thus it is possible to improve the energy density. Theamount of the active material per unit area in an electrode is improved,and thus the over-voltage that increases due to an increase in thecurrent density is mitigated. Accordingly, it is possible to improve thecycle characteristics. In the case where the battery is charged with ahigh charging voltage, the decomposition of the electrolyte solutiontends to occur more. Accordingly, it is possible improve the cyclecharacteristics by suppressing an increase in the over-voltage.

Hereinafter, embodiments of the present disclosure will be describedwith reference to the accompanying drawings. In addition, descriptionwill be made in the following order.

1. First Embodiment (Battery)

2. Second Embodiment (Example of Battery Pack)

3. Third Embodiment (Example of Battery Pack)

4. Fourth Embodiment (Example of Electrical Storage System)

5. Other Embodiments (Modification Example)

In addition, the following embodiments and the like are preferredspecific examples of the present disclosure, and the content of thepresent disclosure is not limited to the embodiments and the like. Inaddition, effects that are described in this specification areillustrative only, and there is no limitation thereto. In addition, itshould be understood that existence of effects different from theexemplified effects is possible.

1. First Embodiment Configuration of Battery

A nonaqueous electrolyte battery (battery) according to a firstembodiment of the present disclosure will be described. FIG. 1illustrates an exploded perspective configuration of the nonaqueouselectrolyte battery according to the first embodiment of the presentdisclosure, and FIG. 2 illustrates an enlarged cross-section taken alongline I-I in a wound electrode body 30 illustrated in FIG. 1.

In the nonaqueous electrolyte battery, mainly, a wound electrode body30, to which a positive electrode lead 31 and a negative electrode lead32 are attached, is accommodated inside a film-shaped exterior packagingmember 40. A battery structure using the film-shaped exterior packagingmember 40 is also referred to as a laminate film type. The nonaqueouselectrolyte battery is, for example, a nonaqueous electrolyte secondarybattery capable of being charged and discharged, and for example, alithium ion secondary battery.

For example, the positive electrode lead 31 and the negative electrodelead 32 are led out from the inside of the exterior packaging member 40toward the outside. The positive electrode lead 31 is constituted by,for example, a metal material such as aluminum, and the negativeelectrode lead 32 is constituted by, for example, a metal material suchas copper, nickel, and stainless steel. For example, the metal materialshave a thin plate shape, or a network shape.

For example, the exterior packaging member 40 has a configuration inwhich a resin layer is provided on both surfaces of a metal layerconstituted by metal foil similar to an aluminum laminate film in whicha nylon film, aluminum foil, and a polyethylene film are bonded in thisorder. As a typical configuration, for example, the exterior packagingmember 40 has a lamination structure of an outer resin layer/a metallayer/an inner resin layer. For example, the exterior packaging member40 has a structure in which outer edge portions of two sheets ofrectangular aluminum laminate films are bonded to each other throughfusion or with an adhesive in such a manner that the inner resin layerfaces the wound electrode body 30. The outer resin layer and the innerresin layer may be constituted by a plurality of layers, respectively.

The metal material that constitutes the metal layer may have a functionas a moisture-permeation resistant barrier film, and aluminum (Al) foil,stainless steel (SUS) foil, nickel (Ni) foil, coated iron (Fe) foil, andthe like may be used as the metal material. Among these, it ispreferable to appropriately use the aluminum foil which is light inweight and is excellent in workability. Particularly, it is preferableto use, for example, annealed aluminum (JIS A8021P-O), (JIS A8079P-O),or (JIS AlN30-O), or the like when considering workability.

Typically, it is preferable that the thickness of the metal layer is setto, for example, 30 μm to 150 μm. In the case of less than 30 μm,material strength tends to decrease. In addition, when exceeding 150 μm,processing is significantly difficult, and the thickness of a laminatefilm 52 increases, and thus a volume efficiency of the nonaqueouselectrolyte battery tends to decrease.

The inner resin layer is a portion that is thermally melted, and partsof the inner resin layer are fused to each other. As the inner resinlayer, polyethylene (PE), casted polypropylene (CPP), polyethyleneterephthalate (PET), low-density polyethylene (LDPE), high-densitypolyethylene (HDPE), linear low-density polyethylene (LLDPE), and thelike can be used, and a plurality of kinds of the materials may beselected and used.

As the outer resin layer, a polyolefin-based resin, a polyamide-basedresin, a polyimide-based resin, polyester, and the like are used whenconsidering beauty in external appearance, toughness, flexibility, andthe like. Specifically, nylon (Ny), polyethylene terephthalate (PET),polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), orpolybutylene naphthalate (PBN) is used, and a plurality of kinds ofthese may be selected and used.

An adhesive film 41, which prevents intrusion of external air, isinserted between the exterior packaging member 40, and the positiveelectrode lead 31 and the negative electrode lead 32. The adhesive film41 is constituted by a material having adhesiveness with respect to thepositive electrode lead 31 and the negative electrode lead 32. Examplesof the material include polyolefin resins such as polyethylene,polypropylene, modified polyethylene, and modified polypropylene.

In addition, the exterior packaging member 40 may be constituted by alaminate film having other lamination structures, a polymer film such aspolypropylene, a metal film, and the like instead of the aluminumlaminate film having the above-described lamination structure.

FIG. 2 illustrates a cross-sectional configuration along line I-I in thewound electrode body 30 illustrated in FIG. 1. The wound electrode body30 has a configuration in which a strip-shaped positive electrode 33 anda strip-shaped negative electrode 34 are laminated on each other andwound through a strip-shaped separator 35 and an electrolyte 36, and theoutermost peripheral portion of the wound electrode body 30 is protectedby a protective tape 37.

(Positive Electrode)

For example, the positive electrode 33 includes a both-surface formingportion in which a positive electrode active material layer 33B isprovided on both surfaces of a positive electrode current collector 33Ahaving one main surface and the other main surface. In addition,although not illustrated, the positive electrode 33 may include asingle-surface forming portion in which the positive electrode activematerial layer 33B is provided only on a single surface of the positiveelectrode current collector 33A. For example, the positive electrodecurrent collector 33A is constituted by metal foil such as aluminumfoil.

The positive electrode active material layer 33B contains one or morekinds of positive electrode materials capable of intercalating anddeintercalating lithium as a positive electrode active material. Thepositive electrode active material layer 33B may include other materialssuch as a binding agent and a conductive agent as necessary.

As the positive electrode material, it is preferable to use a lithiumcobalt composite oxide which has a layered structure, includes at leastlithium and cobalt, and is capable of intercalating and deintercalatinglithium. In the case of using the lithium cobalt composite oxide, adischarging curve is flat (a flat region is large), and an averagevoltage is high. Accordingly, an energy density is large, and a cut-offvoltage is high. The lithium cobalt composite oxide having thecharacteristics is particularly appropriate for the laminate film typegel electrolyte battery of the present disclosure and the like for acellular use (a portable phone, a smart phone) and the like in whichlight weight and a high capacity are demanded. On the other hand, forexample, in a case of using a nickel-based positive electrode activematerial such as LiNiO₂, thermal stability in a charging state, whichdecreases at a final stage of a discharging curve (a flat region isshort), is not good (stability of a battery is relatively not good), thecut-off voltage is low, and a large amount of gas occurs duringhigh-temperature storage. According to this, the nickel-based positiveelectrode active material is not appropriate for the laminate film typegel electrolyte battery according to the first embodiment of the presentdisclosure, and the like.

In addition, as the positive electrode material, in addition to thelithium cobalt composite oxide, other positive electrode activematerials capable of intercalating and deintercalating lithium may beused.

As the lithium cobalt composite oxide, specifically, it is preferable touse a lithium cobalt composite oxide having a composition expressed bythe following General Formula (Chem. 1).Li_(p)Co_((1-q))M1_(q)O_((2-y))X_(z)  (Chem. 1)

(In Formula, M1 represents at least one kind excluding cobalt (Co) amongelements selected from Group 2 to Group 15, and X represents at leastone kind excluding oxygen (O) among elements in Group 16 and elements inGroup 17. p, q, y, and z are values in ranges of 0.9≦p≦1.1, 0≦q<0.5,−0.10≦y≦0.20, and 0≦z≦0.1.)

More specifically, examples of the lithium cobalt composite oxideexpressed by Chem. 1 include Li_(p)CoO₂ (p is the same as describedabove), Li_(p)Co_(0.98)Al_(0.01)Mg_(0.01)O₂ (p is the same as describedabove), and the like.

(Coating Particles)

As the positive electrode material capable of intercalating anddeintercalating lithium, coating particles, which includes particles ofthe above-described lithium cobalt composite oxide and a coating layerprovided at least on a part of the surface of the lithium cobaltcomposite oxide particles which become a base material, may be used.When using the coating particles, it is possible to further improvebattery characteristics.

The coating layer is provided at least on a part of the surface of thelithium cobalt composite oxide particles which become a base material,and has a composition element or a composition ratio that is differentfrom that of the lithium cobalt composite oxide particles which becomethe base material.

Existence of the coating layer can be confirmed by examining aconcentration variation of a constituent element from a surface of thepositive electrode material toward the inside thereof. For example, theconcentration variation can be obtained by measuring a composition ofthe lithium composite oxide particles through auger electronspectroscopy (AES) or secondary ion mass spectrometry (SIMS) whilecutting the lithium composite oxide particles through sputtering or thelike. In addition, the concentration variation can be measured asfollows. The lithium composite oxide particles provided with the coatinglayer is gradually dissolved in an acidic solution, and a variation inan amount of elution with the passage of time is measured throughinductively coupled plasma (ICP) spectrometry or the like.

Examples of the coating layer include a coating layer including anoxide, a transition metal compound, and the like. Specific examples ofthe coating layer include an oxide that includes at least one of lithium(Li), nickel (Ni), and manganese (Mn), a compound that includes at leastone kind selected from the group consisting of nickel (Ni), cobalt (Co),manganese (Mn), iron (Fe), aluminum (Al), magnesium (Mg), and zinc (Zn),oxygen (O), and phosphorus (P), and the like. The coating layer mayinclude a halide such as lithium fluoride, or a chalcogenide other thanoxygen.

The coating layer is provided at least at a part of the lithium cobaltcomposite oxide particles, and may include at least one element Mselected from Group 2 to Group 16, and at least one element X selectedfrom phosphorous (P), silicon (Si), germanium (Ge), and a halogenelement differently from a main transition metal that substantiallyconstitutes a transition metal included in the lithium cobalt compositeoxide particles. In the coating layer, the element M and the element Xmay exhibit distribution profiles different from each other.

Here, the main transition metal, which constitutes the lithium cobaltcomposite oxide particles, represents a transition metal of which aratio is the largest among transition metals that constitute the lithiumcobalt composite oxide particles. For example, in a case of compositeoxide particles in which an average composition isLiCo_(0.98).Al_(0.01)Mg_(0.01)O₂, the main transition metal representscobalt (Co).

The coating layer is a layer that is formed when the element M and/orthe element X is distributed on a surface of transition metal compositeoxide particles. The coating layer is a region in which a compositionratio of the element M and/or the element X in the coating layer ishigher than a composition ratio of the element M and/or the element X inthe transition metal composite oxide particles.

In the coating layer, the element M and the element X which are includedin the coating layer may exhibit distribution profiles different fromeach other in the coating layer. Specifically, it is preferable that theelement M and the element X have a difference in uniformity ofdistribution, and the element M is uniformly distributed on the surfaceof the transition metal composite oxide particles in comparison to theelement X. In addition, it is preferable that the element M isdistributed on the surface of the transition metal composite oxideparticles in an amount that is more than an amount of the element X. Inaddition, the distribution profile of the element M and the element Xcan be confirmed by observing the composite oxide particles having thecoating layer by using a scanning electron microscope (SEM)(hereinafter, referred to as an SEM/EDX) provided with an energydispersive X-ray (EDX) analyzer. In addition, it is also possible toconfirm the distribution profile by performing analysis on the surfaceor the cross-section of the composite oxide particles through time offlight secondary ion mass spectrometry (TOF-SIMS) so as to measure ionsincluding the element M or the element X.

It is preferable that the element M is distributed on the surface of thelithium cobalt composite oxide particles in an approximately uniformmanner to form the coating layer. This is because when the surface ofthe lithium cobalt composite oxide particles is coated with the coatinglayer including the element M, elution of the main transition metalelement included in the lithium cobalt composite oxide particles can besuppressed, or reaction with the electrolyte solution can be suppressed,and thus it is possible to suppress deterioration of the batterycharacteristics.

As the element M, for example, elements in Group 2 to Group 16 which areused for substitution, addition, coating, and the like with respect tolithium cobaltate (LiCoO₂) that has been used for the positive electrodeactive material in the related art.

On the other hand, it is preferable that the coating layer is formed insuch a manner that the element X is scattered on the surface of thelithium cobalt composite oxide particles. This is because it is possibleto suppress a decrease in intercalation and deintercalation of lithiumdue to the coating layer including the element X. In addition, forexample, the element X may be unevenly distributed on the surface of thecomposite oxide particles, or may scatter on the entirety of the surfaceat a plurality of sites. In addition, the element X may be distributedon the coating layer including the element M in a scattering manner.

In addition, the element X is at least one element selected fromphosphorous (P), silicon (Si), germanium (Ge), and a halogen element.These elements are less likely to be solid-soluted in the compositeoxide particles, and are capable of suppressing occurrence of a gas dueto formation of a stable compound with lithium.

Here, an element ratio of cobalt (Co), the element X, and the element Min the surface of the positive electrode active material can be measuredby using a scanning X-ray photoelectron spectroscopy analyzer (ESCA)(QuanteraSXM, manufactured by ULVAC-PHI, Incorporated). Specifically, aparticle sample to be measured is buried in a metal indium specimen, thesample specimen is fixed to a sample stage by using a plate spring, andthen measurement is performed. As an X-ray source, monochromatic Al—Kαrays (1486.6 eV) are used, and the measurement can be performed whileperforming charging compensation with respect to the surface of themeasurement sample in an automatic mode by using an argon ion gun and anelectron neutralizing gun.

A method of forming the coating layer is not particularly limited. Forexample, it is possible to use a method in which a raw material of thecoating layer is deposited to the lithium cobalt composite oxideparticles which become core particles by using an apparatus that appliesa compressive shear stress such as mechanofusion, and then a heattreatment is performed to form the coating layer, a method in which ahydroxide that becomes a precursor of the coating layer is deposited tothe lithium cobalt composite oxide particles by using neutralizationtitration, and then a heat treatment is performed to form the coatinglayer, and the like.

In addition, the coating layer is not limited to the above-describedconfiguration. The coating layer may have a composition element or acomposition ration that is different from that of the lithium cobaltcomposite oxide particles, and at least a part of the surface of thelithium cobalt composite oxide particles may be coated with the coatinglayer.

(Conductive Agent)

As the conductive agent, for example, a carbon material such as carbonblack and graphite is used.

(Binding Agent)

Examples of the binding agent that is used include a resin material suchas polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE),polyacrylonitrile (PAN), styrene-butadiene rubber (SBR), andcarboxymethyl cellulose (CMC), and at least one kind that is selectedfrom copolymers containing the resin material as a main component, andthe like.

(Area Density of Positive Electrode Active Material Layer)

For example, an area density S (mg/cm²) of the positive electrode activematerial layer 33B is set to 27 mg/cm² or greater from the viewpoint ofa high capacity. In addition, when using the separator having apredetermined structure of the present disclosure, the area density S(mg/cm²) of the positive electrode active material layer 33B isincreased, and thus an over-voltage is mitigated. Accordingly, it ispossible to improve cycle characteristics.

In addition, in the positive electrode 33, the area density S (mg/cm²)of the positive electrode active material layer 33B represents the totalmass of the mass of the positive electrode active material layer 33B perarea (1 cm²) on one surface side and the mass of the positive electrodeactive material layer 33B per area (1 cm²) on the other surface side inthe portion (both-surface forming portion) provided with the positiveelectrode active material layer 33B on the both surfaces of the positiveelectrode current collector 33A. For example, the area density S(mg/cm²) of the positive electrode active material layer 33B can bemeasured as follows.

(Method of Measuring Area Density S (mg/cm²) of Positive ElectrodeActive Material)

After a battery is completely discharged, the battery is disassembled totake out a positive electrode plate (the positive electrode 33). Thepositive electrode plate is cleaned with a solvent (for example,dimethyl carbonate (DMC)), and is sufficiently dried. A portion(both-surface forming portion) of the positive electrode plate, in whichthe positive electrode active material layer 33B is formed on bothsurfaces of the positive electrode current collector 33A, is punched ina predetermined area (cm²) (referred to as a punching area) to measurethe mass (mg) (referred to as mass A), and then a portion of thepositive electrode plate, in which a mixture layer is not applied toboth surfaces, is also punched to measure mass (mg) (referred to as massB). In addition, the area density is calculated by the followingcalculation formula.Area density S(mg/cm²)=(mass A−mass B)÷punching area  Calculationformula:

(Negative Electrode)

For example, the negative electrode 34 has a structure provided with aboth-surface forming portion in which a negative electrode activematerial layer 34B is provided on both surfaces of the negativeelectrode current collector 34A having one main surface and the othermain surface. In addition, although not illustrated, the negativeelectrode 34 may include a single-surface forming portion in which thenegative electrode active material layer 34B is provided only on asingle surface of the negative electrode current collector 34A. Forexample, the negative electrode current collector 34A is constituted bymetal foil such as copper foil.

The negative electrode active material layer 34B contains one or morekinds of negative electrode materials capable of intercalating anddeintercalating lithium as a negative electrode active material. As isthe positive electrode active material layer 33B, the negative electrodeactive material layer 34B may include other materials such as aconductive agent and a binding agent as necessary.

In addition, in the battery, the electrochemical equivalent of thenegative electrode material capable of intercalating and deintercalatinglithium is greater than the electrochemical equivalent of the positiveelectrode 33, and theoretically, the electrochemical equivalent of thenegative electrode material is set in order for a lithium metal not toprecipitate to the negative electrode 34 during charging.

Examples of the negative electrode material capable of intercalating anddeintercalating lithium include carbon materials such as hardlygraphitizable carbon, easily graphitizable carbon, graphite, pyrolyticcarbons, cokes, glass-like carbons, an organic polymer compound firedbody, carbon fiber, and activated charcoal. Among these, examples of thecokes include pitch cokes, needle cokes, petroleum cokes, and the like.The organic polymer compound fired body represents a polymer materialsuch as a phenol resin and a furan resin is fired at an appropriatetemperature for carbonization, and may be partially classified into thehardly graphitizable carbon and the easily graphitizable carbon. Thecarbon materials are preferable when considering that a variation in acrystal structure which occurs during charging and discharging is verysmall, a high charging and discharging capacity can be obtained, andsatisfactory cycle characteristics can be obtained. Particularly, thegraphite is preferable when considering that the electrochemicalequivalent is large and a high energy density can be obtained. Inaddition, the hardly graphitizable carbon is preferable when consideringthat excellent cycle characteristics can be obtained. In addition, acarbon material, in which a charging and discharging potential is low,specifically, the charging and discharging potential is close to that ofa lithium metal, is preferable when considering that high-energydensification of a battery can be easily realized.

Examples of the negative electrode material capable of intercalating anddeintercalating lithium also include a material which is capable ofintercalating and deintercalating lithium and which includes at leastone kind of a metal element and a metalloid element as a constituentelement. This is because when using the material, it is possible toobtain a high energy density. Particularly, it is more preferable to usethe material in combination with the carbon material when consideringthat a high-energy density can be obtained, and excellent cyclecharacteristics can be obtained. The negative electrode material may bean elementary substance of the metal element or the metalloid element,an alloy thereof, a compound thereof, or a material that includes one ormore phases thereof at least at a part. In addition, in the presentdisclosure, examples of the alloy include an alloy including one or morekinds of metal elements and one or more kinds of metalloid elements inaddition to alloy that is constituted by two or more kinds of metalelements. In addition, the alloy may include a non-metal element. Thetexture of the alloy includes a solid solution, a eutectic crystal (aeutectic mixture), an intermetallic compound, and a texture in which twoor more kinds of these textures coexist.

Examples of the metal element or the metalloid element which constitutesthe negative electrode material include a metal element or a metalloidelement which is capable of forming an alloy in combination withlithium. In addition, the negative electrode material including theelement capable of forming an alloy in combination with lithium isreferred to as an alloy-based negative electrode. Specific examples ofthe metal element or the metalloid element, which is capable of formingan alloy in combination with lithium, include magnesium (Mg), boron (B),aluminum (Al), titanium (Ti), gallium (Ga), indium (In), silicon (Si),germanium (Ge), tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd), silver(Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), yttrium (Y), palladium(Pd), and platinum (Pt). These may be crystalline materials or amorphousmaterials.

As the negative electrode material, for example, materials including ametal element or a metalloid element in group 4B in a short-period typeperiodic table as a constituent element are preferable, materialsincluding at least one of silicon (Si) and tin (Sn) as a constituentelement are more preferable, and materials including at least silicon isstill more preferable. This is because silicon (Si) and tin (Sn) havelarge capacity of intercalating and deintercalating lithium and mayobtain a high energy density. Examples of the negative electrodematerial, which includes at least one kind of silicon and tin, includean elementary substance of silicon, an alloy or a compound thereof, anelementary substance of tin, an alloy or a compound thereof, and amaterial that includes one or more kinds of phases of these at least ata part.

Examples of the alloy of silicon include alloys including at least onekind selected from the group consisting of tin (Sn), nickel (Ni), copper(Cu), iron (Fe), cobalt (Co), manganese (Mn), zinc (Zn), indium (In),silver (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb),and chromium (Cr) as a secondary constituent element other than silicon.Examples of the alloy of tin include alloys including at least one kindselected from the group consisting of silicon (Si), nickel (Ni), copper(Cu), iron (Fe), cobalt (Co), manganese (Mn), zinc (Zn), indium (In),silver (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb),and chromium (Cr) as a secondary constituent element other than tin(Sn).

Examples of the compound of tin (Sn) or silicon (Si) include compoundsincluding oxygen (O) or carbon (C). Furthermore, the compounds of tin orsilicon may include the above-described secondary constituent element inaddition to tin (Sn) or silicon (Si).

Among these, as the negative electrode material, a SnCoC-containingmaterial, which includes cobalt (Co), tin (Sn), and carbon (C) as aconstituent element, and in which an amount of carbon is 9.9 mass % to29.7 mass %, a ratio of cobalt (Co) on the basis of the sum of tin (Sn)and cobalt (Co) is 30 mass % to 70 mass %, is preferable. This isbecause a high energy density and excellent cycle characteristics can beobtained in this composition range.

The SnCoC-containing material may further include another constituentelement as necessary. As another constituent element, for example,silicon (Si), iron (Fe), nickel (Ni), chrome (Cr), indium (In), niobium(Nb), germanium (Ge), titanium (Ti), molybdenum (Mo), aluminum (Al),phosphorus (P), gallium (Ga), or bismuth (Bi) is preferable, and theSnCoC-containing material may include two or more kinds of theseconstituent elements. This is because the capacity or cyclecharacteristics can be further improved.

In addition, the SnCoC-containing material has a phase including tin(Sn), cobalt (Co), and carbon (C), and it is preferable that this phasehave a low crystalline or amorphous structure. In addition, in theSnCoC-containing material, it is preferable that at least a part ofcarbon (C) as a constituent element is bonded to a metal element or ametalloid element as another constituent element. The reason for thepreference is as follows. A decrease in cycle characteristics isconsidered to be due to aggregation or crystallization of tin (Sn) orthe like, but when carbon (C) is bonded to another element, theaggregation or crystallization can be suppressed.

Examples of the measurement method of examining the bonding state of theelement include X-ray photoelectron spectroscopy (XPS). In the XPS, in acase of graphite, a peak of the 1s orbital (C1s) of carbon is shown at284.5 eV in a device subjected to energy calibration such that a peak ofthe 4f orbital (Au4f) of a gold atom is obtained at 84.0 eV. Inaddition, in a case of surface-contaminated carbon, the peak is shown at284.8 eV. In contrast, in a case where the charge density of the carbonatom increases, for example, in a case where carbon is bonded to themetal element or the metalloid element, the C1s peak is shown in aregion below 284.5 eV. That is, in a case where a peak of a syntheticwave of C1s, which is obtained for the SnCoC-containing material, isshown in a region below 284.5 eV, at least a part of the carbon includedin the SnCoC-containing material is in a state of being bonded to themetal element or the metalloid element present as another constituentelement.

In addition, in the XPS measurement, for example, the C1s peak is usedfor calibration of an energy axis of a spectrum. Typically,surface-contaminated carbon is present on the surface of theSnCoC-containing material, and thus the C1s peak of thesurface-contaminated carbon is set to 284.8 eV, and this is used as anenergy reference. In the XPS measurement, a waveform of the C1s peak isobtained as a type that includes both of the peak of thesurface-contaminated carbon and the peak of the carbon in theSnCoC-containing material. Therefore, the peak of thesurface-contaminated carbon and the peak of the carbon in theSnCoC-containing material are separated from each other, for example,through analysis conducted using commercially available software. In thewaveform analysis, the position of a main peak present on the minimumbinding energy side is used as an energy reference (284.8 eV).

In addition, examples of the negative electrode material capable ofintercalating and deintercalating lithium also include a metal oxide, apolymer compound, and the like which are capable of intercalating anddeintercalating lithium. Examples of the metal oxide include lithiumtitanate (Li₄Ti₅O₁₂), iron oxide, ruthenium oxide, molybdenum oxide, andthe like. Examples of the polymer compound include polyacetylene,polyaniline, polypyrrole, and the like.

In addition, the negative electrode material capable of intercalatingand deintercalating lithium may be a material other than theabove-described materials. In addition, two or more kinds of theabove-described negative electrode materials may be mixed in anarbitrary combination.

For example, the negative electrode active material layer 34B may beformed by any one of a vapor phase method, a liquid phase method, athermal spraying method, a firing method, and an application method, andtwo or more kinds of the methods may be combined. In the case of formingthe negative electrode active material layer 34B by the vapor phasemethod, the liquid phase method, the thermal spraying method, the firingmethod, or two or more kinds of the methods, it is preferable thatalloying of the negative electrode active material layer 34B and thenegative electrode current collector 34A occurs at least on a part of aninterface thereof. Specifically, it is preferable that at the interface,the constituent element of the negative electrode current collector 34Ais diffused to the negative electrode active material layer 34B, theconstituent element of the negative electrode active material layer 34Bis diffused to the negative electrode current collector 34A, or theconstituent elements are diffused to each other. This is because it ispossible to suppress fracture due to expansion and shrinkage of thenegative electrode active material layer 34B in accordance with chargingand discharging, and it is possible to improve electron conductivitybetween the negative electrode active material layer 34B and thenegative electrode current collector 34A.

In addition, examples of the vapor phase method include a physicaldeposition method or a chemical deposition method. Specific examples ofthe vapor phase method include a vacuum deposition method, a sputteringmethod, an ion plating method, a laser ablation method, thermochemicalvapor deposition (CVD; chemical vapor deposition) method, a plasmachemical vapor deposition method, and the like. As the liquid phasemethod, a known method such as electroplating and electroless platingcan be used. The firing method is a method in which for example, aparticle-like negative electrode active material is mixed with a bindingagent and the like, the resultant mixture is dispersed in a solvent, andafter application, a heat treatment is performed at a temperature thatis higher than a melting point of the binding agent and the like. Withregard to the firing method, a known method can be used, and examples ofthe firing method include an atmosphere firing method, a reactive firingmethod, a hot press firing method, and the like.

(Separator)

The separator 35 has a configuration including at least a porous film 35a. Examples of the separator 35 include a first separator 35, a secondseparator 35, and the like. FIG. 3A illustrates a configuration exampleof the first separator 35. FIG. 3B illustrates a configuration exampleof the second separator 35.

(First Separator)

As illustrated in FIG. 3A, the first separator 35 is constituted by onlythe porous film 35 a.

(Porous Film)

The porous film 35 a has a structure satisfying the followingExpressions0.04≦Ri≦−0.07L−0.09×S+4.99Ri=τ ² L/ε′ε′=[{(L×ε/100)−Rz×0.46/3}/L]×100τ={(1.216×ε′Td×10⁻⁴)/L} ^(0.5)  (Expressions)

[provided that, Ri: a film resistance (μm), L: a film thickness (μm), τ:a tortuosity factor, T: air permeability (sec/100 cc), d: a pore size(nm), Rz: a surface roughness maximum height (the sum of values of afront surface and a rear surface) (μm), ε: porosity (%), ε′: correctedporosity (%), and S: the area density of the positive electrode activematerial layer (mg/cm²)]

In addition, as described above, the area density S (mg/cm²) of thepositive electrode active material layer 33B is 27 mg/cm² or greater. Inaddition, in consideration of a range in which the above-describedexpressions are satisfied, it is preferable that the area density S(mg/cm²) of the positive electrode active material layer 33B is 51mg/cm² or less.

The respective parameters in the expressions can be measured as follows.In addition, description has been given to the measurement of the areadensity of the positive electrode active material layer, and thus thedescription will be omitted.

(Pore Size d)

The pore size d (nm) is an average pore size that is measured by usingnon-mercury Palm Polo meter (product name: IEP-200-A) manufactured bySEIKA Corporation.

(Surface Roughness Maximum Height Rz)

The surface roughness maximum height Rz (μm) can be measured inaccordance with JIS B0601 by using a nano-scale hybrid microscope(product name: VN-8000) manufactured by KEYENCE Corporation. Inaddition, the surface roughness maximum height Rz (μm) is the sum ofvalues obtained by performing measurement with respect to two mainsurfaces (a front surface and a rear surface) of the porous film 35 a.

(Porosity ε)

The porosity ε (%) of the porous film 35 a can be measured by using agravimetric method. In this method, 10 sites of the porous film 35 a arepunched toward a thickness direction of the porous film 35 a in acircular shape having a diameter of 2 cm, and the thickness h of thecentral portion of the punched circular film and the mass w of the filmare measured, respectively. In addition, a volume V corresponding to 10sheets of films and mass W corresponding to 10 sheets of films arecalculated by using the thickness h and the mass w, and the porosity ε(%) can be calculated by the following expression.Porosity ε(%)={(ρV−W)/(ρV)}×100

Here, ρ represents a density of a material of the porous film 35 a.

(Air Permeability T)

The air permeability T (sec/100 cc) is Gurley permeability. The Gurleypermeability can be measured in accordance with JIS P8117. The Gurleypermeability represents the number of seconds taken for 100 cc of air topass through a membrane at a pressure of 1.22 kPa.

(Film Thickness L)

The film thickness L is an average film thickness that is obtained bymeasuring film thickness of two sheets of the porous films 35 a, whichare overlapped to each other at a load of 1N, at five sites with a probeof φ5 mm by using a probe type film thickness meter (DIGITAL GUAGESTANDDZ-501, manufactured by Sony corporation), and by calculating theaverage of measured values/2.

(Corrected Porosity ε′)

The corrected porosity ε′ can be calculated from measured values of thefilm thickness L, the porosity ε, the pore size d, and the surfaceroughness maximum height Rz by using the following Expression (A).Corrected porosity ε′(%)=[{(L×ε/100)−Rz×0.46/3}/L]×100  Expression (A).

[provided that, L: film thickness (μm), ε: porosity (%), Rz: the surfaceroughness maximum height (the sum of values of a front surface and arear surface) (μm)]

(Tortuosity Factor τ)

The tortuosity factor τ can be calculated from measured values of theair permeability T, the corrected porosity ε′, the pore size d, and thefilm thickness L by using the following Expression (B).Tortuosity factor τ={(1.216×ε′Td×10⁻⁴)/L} ^(0.5)  Expression (B)

[provided that, L: film thickness (μm), ε′: corrected porosity (%), T:air permeability (sec/100 cc)]

(Film Resistance Ri)

The film resistance Ri (μm) can be calculated from measured values ofthe corrected porosity ε′, the film thickness L, and the tortuosityfactor τ by using the following Expression (C).Ri=τ ² L/ε′  Expression (C)

[provided that, L: film thickness (μm), ε′: corrected porosity (%), τ:tortuosity factor]

As the resin material that constitutes the porous film 35 a, forexample, a polyolefin resin such as polypropylene and polyethylene, anacrylic resin, a styrene resin, a polyester resin, a nylon resin, andthe like can be used. Among these, it is preferable to use thepolyolefin resin (polyolefin film) which tends to form a structuresatisfying Expression (1), is excellent in a short-circuit preventioneffect, and is capable of improving battery stability due to a shut-downeffect. In addition, the porous film 35 a may have a structure in whicha resin layer formed from a resin material is laminated in two or morelayers. The porous film 35 a may be a resin film that is formed bymelting and kneading two or more kinds of resin materials. The porousfilm 35 a may include an additive such as an antioxidant.

(Method of Preparing Porous Film)

For example, the porous film 35 a can be prepared as follows. Forexample, a uniform solution prepared by mixing a polymer such as apolyolefin resin and a solvent (plasticizer) at a high temperature ismade into a film by using a T die method, an inflation method, and thelike, and the film is stretched. Then, the solvent is extracted andremoved by using another volatile solvent, whereby the porous film 35 ais formed. As the solvent, nonvolatile organic solvents that dissolve apolymer at a high temperature are used alone, or the nonvolatile organicsolvents are mixed and used. A phase separation type varies due to acombination of the polymer and the solvent, and thus a porous structurealso varies. With regard to a stretching method, sequential biaxialstretching by roll stretching and tenter stretching, simultaneousbiaxial stretching by simultaneous biaxial tenter, and the like can beapplied. In a manufacturing process, for example, at least any one of anamount of a plasticizer, a stretching ratio, and a stretchingtemperature is adjusted to obtain the porous film 35 a having a desiredstructure satisfying the expressions. In addition, the method ofmanufacturing the porous film 35 a is not limited to the above-describedexample.

(Thickness of Separator)

The thickness Ltotal (=the thickness L of the porous film) of the firstseparator 35 may be set in an arbitrary manner as long as the thicknessis equal to or larger than a thickness with which necessary strength canbe maintained. For example, it is preferable to set the thickness Ltotalof the first separator 35 to a thickness with which insulation betweenthe positive electrode 33 and the negative electrode 34 is accomplishedfor prevention of short-circuiting and the like, ion permeability for anappropriate battery reaction through the first separator 35 is provided,volume efficiency of an active material layer that contributes to thebattery reaction in the battery is increased as much as possible.Specifically, it is preferable that the thickness Ltotal of the firstseparator 35 is, for example, 3 μm to 17 μm.

When the thickness Ltotal of the first separator 35 is greater than−0.0873S²+6.9788S−122.66 [S: area density (mg/cm²) of the positiveelectrode active material layer] μm, an electrode length becomes shortdue to an increase in the thickness Ltotal of the first separator 35,and thus a total amount of an active material in the battery decreases.As a result, an effect of a decrease in capacity tends to furtherincrease. According to this, it is more preferable that the thicknessLtotal of the first separator is −0.0873S²+6.9788S−122.66 [S: areadensity (mg/cm²) of the positive electrode active material layer] μm orless when considering that a volume energy density can be furtherincreased (for example, 300 Wh/L or greater).

(Porosity)

For example, the porosity ε of the porous film 35 a is preferably 20% orgreater from the viewpoint of securing satisfactory ion conductivity, ispreferably 57% or less from the viewpoint of maintaining physicalstrength so as to suppress occurrence of short-circuit, and morepreferably 25% to 46%.

(Air Permeability)

The air permeability T of the porous film 35 a is preferably 50 sec/100cc or greater from the viewpoint of maintaining physical strength so asto suppress occurrence of short-circuit, is preferably 1000 sec/100 ccor less from the viewpoint of securing satisfactory ion conductivity,and more preferably 50 sec/100 cc to 500 sec/100 cc.

(Second Separator)

As illustrated in FIG. 3B, the second separator 35 includes the porousfilm 35 a and a surface layer 35 b that is provided at least on onesurface of the porous film 35 a. In addition, FIG. 3B illustrates anexample in which the surface layer 35 b is provided on one surface ofthe porous film 35 a. Although not illustrated, the surface layer 35 bmay be provided on both surfaces of the porous film 35 a.

(Porous Film 35 a)

The porous film 35 a has the configuration as described above.

(Surface Layer)

The surface layer 35 b includes a resin material.

(Resin Material)

For example, the resin material may be fibrillated, and may have athree-dimensional network structure in which fibrils are continuouslyconnected to each other.

Examples of the resin material, which is included in the surface layer35 b, include fluorine-containing resins such as polyvinylidene fluorideand polytetrafluoroethylene, fluorine-containing rubbers such as avinylidene fluoride-tetrafluoroethylene copolymer and anethylene-tetrafluoroethylene copolymer, a styrene-butadiene copolymerand a hydride thereof, an acrylonitrile-butadiene copolymer and ahydride thereof, an acrylonitrile-butadiene-styrene copolymer and ahydride thereof, a methacrylic ester-acrylic ester copolymer, astyrene-acrylic ester copolymer, an acrylonitrile-acrylic estercopolymer, an ethylene propylene rubber, polyvinyl acetate, cellulosederivatives such as ethyl cellulose, methyl cellulose, hydroxyethylcellulose, and carboxymethyl cellulose, resins such as polyphenyleneether, polysulfone, polyether sulfone, polyphenylene sulfide,polyetherimide, polyimide, polyamide (particularly, aramid),polyamideimide, polyacrylonitrile, polyvinyl alcohol, polyether, anacrylic resin, and polyester in which at least one of a melting pointand a glass transition temperature is 180° C. or higher, thermosettingresins such as a phenol resin and an epoxy resin, and the like.

In addition, the surface layer 35 b may further include particles suchas inorganic particles and organic particles. In this case, the resinmaterial is contained in the surface layer 35 b so as to bind theparticles to the surface of the porous film 35 a or bind the particlesto each other. The particles may be carried in a resin material having athree-dimensional network structure. In this case, it is possible tomaintain a state in which the particles are not connected to each otherand are dispersed. In addition, the resin material that is notfibrillated may bind the surface of the porous film 35 a and theparticles. In this case, a higher binding property can be obtained.

(Inorganic Particle)

Examples of the inorganic particles include a metal oxide, a metal oxidehydrate, a metal hydroxide, a metal nitride, a metal carbide, and ametal sulfide which are insulating inorganic particles. As the metaloxide and the metal oxide hydrate, aluminum oxide (alumina, Al₂O₃),boehmite (Al₂O₃H₂O or AlOOH), magnesium oxide (magnesia, MgO), titaniumoxide (titania, TiO₂), zirconium oxide (zirconia, ZrO₂), silicon oxide(silica, SiO₂) or yttrium oxide (yttria, Y₂O₃), zinc oxide (ZnO), andthe like can be appropriately used. As the metal nitride, siliconnitride (Si₃N₄), aluminum nitride (AlN), boron nitride (BN), titaniumnitride (TiN), and the like can be appropriately used. As the metalcarbide, silicon carbide (SiC), boron carbide (B₄C), and the like can beappropriately used. As the metal sulfide, barium sulfate (BaSO₄) and thelike can be appropriately used. As the metal hydroxide, aluminumhydroxide (Al(OH)₃), and the like can be used. In addition, silicateincluding porous aluminum silicate such as zeolite(M_(2/n)O.Al₂O₃.xSiO₂.yH₂O, M represents a metal element, x≧2, y≧0), andlayered silicate such as talc (Mg₃Si₄O₁₀(OH)₂), and a mineral such asbarium titanate (BaTiO₃) and strontium titanate (SrTiO₃) may be used. Inaddition, lithium compounds such as Li₂O₄, Li₃PO₄, and LiF also may beused. Carbon materials such as graphite, carbon nanotube, and diamondalso may be used. Among these, it is preferable to use alumina,boehmite, talc, titania (particularly, titania having a rutile typestructure), silica, or magnesia, and more preferably alumina andboehmite.

These inorganic particles may be used alone or two or more kinds thereofmay be mixed and used. The shape of the inorganic particles is notparticularly limited, and a spherical shape, a fibrous shape, a needleshape, a squamous shape, a plate shape, a random shape, and the like maybe used.

(Organic Particles)

Examples of a material that constitute the organic particles includefluorine-containing resins such as polyvinylidene fluoride andpolytetrafluoroethylene, fluorine-containing rubbers such as avinylidene fluoride-tetrafluoroethylene copolymer and anethylene-tetrafluoroethylene copolymer, a styrene-butadiene copolymerand a hydride thereof, an acrylonitrile-butadiene copolymer and ahydride thereof, an acrylonitrile-butadiene-styrene copolymer and ahydride thereof, a methacrylic ester-acrylic ester copolymer, astyrene-acrylic ester copolymer, an acrylonitrile-acrylic estercopolymer, an ethylene propylene rubber, polyvinyl acetate, cellulosederivatives such as ethyl cellulose, methyl cellulose, hydroxyethylcellulose, and carboxymethyl cellulose, resins such as polyphenyleneether, polysulfone, polyether sulfone, polyphenylene sulfide,polyetherimide, polyimide, polyamide such as wholly aromatic polyamide(aramid), polyamideimide, polyacrylonitrile, polyvinyl alcohol,polyether, an acrylic resin, and polyester in which at least one of amelting point and a glass transition temperature is 180° C. or higherand thus high heat resistance is provided, thermosetting resins such asa phenol resin and an epoxy resin, and the like. These materials may beused alone or two or more kinds thereof may be mixed and used. The shapeof the organic particles is not particularly limited, and any one of aspherical shape, a fibrous shape, a needle shape, a squamous shape, aplate shape, a random shape, and the like may be used.

For example, the surface layer 35 b can be obtained as follows.Specifically, the resin material is added to a dispersion solvent suchas N-methyl-2-pyrrolidone to dissolve the resin material, therebyobtaining a resin solution. The resin solution is applied to at leastone surface of the porous film 35 a, and the porous film 35 a issubjected to drying and the like, thereby obtaining the surface layer 35b. In a case where the surface layer 34 b contains particles incombination with the resin material, for example, the surface layer 35 bcan be obtained as follows. Specifically, the resin material and theparticles are mixed with each other, and the resultant mixture is addedto a dispersion solvent such as N-methyl-2-pyrrolidone to dissolve theresin material, thereby obtaining a resin solution. Then, the resinsolution is applied to at least one surface of the porous film 35 a, andthe porous film 35 a is subjected to drying and the like, therebyobtaining the surface layer 35 b.

(Thickness of Separator)

The thickness Ltotal of the second separator 35 (the sum of thethickness L of the porous film 35 a and the thickness of the surfacelayer 35 b) may be set in an arbitrary manner as long as the thicknessis equal to or larger than a thickness with which necessary strength canbe maintained. For example, it is preferable to set the thickness Ltotalof the second separator 35 to a thickness with which insulation betweenthe positive electrode 33 and the negative electrode 34 is accomplishedfor prevention of short-circuiting and the like, ion permeability for anappropriate battery reaction through the second separator 35 isprovided, volume efficiency of an active material layer that contributesto the battery reaction in the battery is increased as much as possible.Specifically, it is preferable that the thickness Ltotal of the secondseparator 35 is, for example, 3 μm to 17 μm.

When the thickness Ltotal of the second separator 35 is greater than−0.0873S²+6.9788S−122.66 [S: area density (mg/cm²) of the positiveelectrode active material layer] μm, an electrode length becomes shortdue to an increase in the thickness Ltotal of the second separator 35,and thus a total amount of an active material in the battery decreases.As a result, an effect of a decrease in capacity tends to furtherincrease. According to this, it is more preferable that the thicknessLtotal of the second separator 35 is −0.08735S²+6.9788S−122.66 [S: areadensity (mg/cm²) of the positive electrode active material layer] μm orless when considering that a volume energy density can be furtherincreased (for example, 300 Wh/L or greater).

(Electrolyte)

The electrolyte 36 includes a nonaqueous electrolyte solution(electrolyte solution) and a polymer compound (matrix polymer compound)that retains the nonaqueous electrolyte solution. For example, theelectrolyte 36 is a so-called gel-like electrolyte. The gel-likeelectrolyte is preferable when considering that high ion conductivity(for example, 1 mS/cm or greater at room temperature) is obtained andliquid leakage is prevented. In addition, the electrolyte 36 may furtherinclude particles such as inorganic particles and organic particles.Details of the inorganic particles and the organic particle are the sameas described above.

(Nonaqueous Electrolyte Solution)

The nonaqueous electrolyte includes an electrolyte salt and a nonaqueoussolvent that dissolves the electrolyte salt.

For example, the electrolyte salt contains one or more kinds of lightmetal compounds such as a lithium salt. Examples of the lithium saltinclude lithium hexafluorophosphate (LiPF₆), lithium tetrafluoroborate(LiBF₄), lithium perchlorate (LiClO₄), lithium hexafluoroarsenate(LiAsF₆), lithium tetraphenylborate (LiB(C₆H₅)₄), lithiummethanesulfonate (LiCH₃SO₃), lithium trifluoromethanesulfonate(LiCF₃SO₃), lithium tetrachloroaluminate (LiAlCl₄), dilithiumhexafluorosilicate (Li₂SiF₆), lithium chloride (LiCl), lithium bromide(LiBr), and the like. Among these, at least one kind among lithiumhexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, andlithium hexafluoroarsenate is preferable, and lithiumhexafluorophosphate is more preferable.

Examples of the nonaqueous solvent include lactone-based solvents suchas γ-butyrolactone, γ-valerolactone, δ-valerolactone, andε-caprolactone, carbonic acid ester-based solvents such as ethylenecarbonate, propylene carbonate, butylene carbonate, vinylene carbonate,dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate,ether-based solvents such as 1,2-dimethoxyethane,1-ethoxy-2-methoxyethane, 1,2-diethoxyethane, tetrahydrofuran,2-methyltetrahydrofuran, nitrile-based solvents such as acetonitrile,sulfolane-based solvents, phosphoric acids, phosphoric acid estersolvents, and nonaqueous solvents such as pyrrolidones. Any one kind ofthe nonaqueous solvents may be used alone, or two or more kinds thereofmay be mixed and used.

In addition, as the nonaqueous solvent, it is preferable to use amixture obtained by mixing cyclic carbonic acid ester and chain carbonicacid ester. It is more preferable to include a compound in which a partor the entirety of hydrogen in cyclic carbonic acid ester and chaincarbonic acid ester is fluorinated. As the fluorinated compound, it ispreferable to use fluoroethylene carbonate(4-fluoro-1,3-dioxolane-2-one: FEC) or difluoro ethylene carbonate(4,5-difluoro-1,3-dioxolane-2-one: DFEC). This is because even in thecase of using the negative electrode 34 including compounds of silicon(Si), tin (Sn), germanium (Ge), and the like as the negative electrodeactive material, it is possible to improve charging and dischargingcycle characteristics. Among these, it is preferable to use difluoroethylene carbonate as the nonaqueous solvent. This is because an effectof improving cycle characteristics is excellent.

(Polymer Compound)

As the polymer compound, a polymer compound that is compatible with thesolvent, and the like can be used. Examples of the polymer compoundinclude polyacrylonitrile, polyvinylidene fluoride, a copolymer ofvinylidene fluoride and hexafluoropropylene, polytetrafluoroethylene,polyhexafluoropropylene, polyethylene oxide, polypropylene oxide,polyphosphazene, polysiloxane, polyvinyl acetate, polyvinyl alcohol,polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, astyrene-butadiene rubber, a nitrile-butadiene rubber, polystyrene,polycarbonate, and the like. These may be used along or a plurality ofkinds thereof may be mixed. Among these, polyacrylonitrile,polyvinylidene fluoride, polyhexafluoropropylene, or polyethylene oxideis preferable. This is because these materials are electrochemicallystable.

(Method of Manufacturing Battery)

For example, the nonaqueous electrolyte battery is manufactured by thefollowing three kinds of manufacturing methods (first to thirdmanufacturing methods).

(First Manufacturing Method)

In the first manufacturing method, first, for example, a positiveelectrode material, a conductive agent, and a binding agent are mixedwith other to prepare a positive electrode mixture. The positiveelectrode mixture is dispersed in a solvent such asN-methyl-2-pyrolidone to prepare a paste-like positive electrode mixtureslurry. Next, the positive electrode mixture slurry is applied to bothsurfaces of the positive electrode current collector 33A, and thesolvent is dried. Then, the positive electrode mixture slurry that isapplied is compression-molded by roll pressing machine and the like soas to form the positive electrode active material layer 33B, therebypreparing the positive electrode 33. In addition, in acompression-molding process, the compression-molding may be performed byusing a roll pressing machine and the like while performing heating asnecessary to adjust thickness and density. According to this, it ispossible to adjust the area density of the positive electrode activematerial layer 33B. In this case, the compression-molding may berepeated a plurality of times.

A negative electrode material and a binding agent are mixed with eachother to prepare a negative electrode mixture, and the negativeelectrode mixture is dispersed in a solvent such asN-methyl-2-pyrolidone to prepare a paste-like negative electrode mixtureslurry. Next, the negative electrode mixture slurry is applied to bothsurfaces of the negative electrode current collector 34A, and thesolvent is dried. Then, the negative electrode mixture slurry that isapplied is compression-molded by a roll pressing machine so as to formthe negative electrode active material layer 34B, thereby preparing thenegative electrode 34.

Next, a precursor solution including an electrolyte solution, a polymercompound, and a solvent is prepared, and is applied to both surfaces ofat least one of the positive electrode 33 and the negative electrode 34.Then, the solvent is evaporated to form the gel-like electrolyte 36.Then, the positive electrode lead 31 is attached to the positiveelectrode current collector 33A, and the negative electrode lead 32 isattached to the negative electrode current collector 34A. In addition,the configuration may be changed in such a manner that the gel-likeelectrolyte 36 is formed on both surfaces of the electrodes and thegel-like electrolyte 36 is formed on at least one surface between bothsurfaces of the separator.

Then, the positive electrode 33 and the negative electrode 34 on whichthe electrolyte 36 is formed are laminated through the separator 35, andare wound in a longitudinal direction. The protective tape 37 is bondedto the outermost peripheral portion of the resultant wound body toprepare a wound electrode body 30. Finally, for example, the woundelectrode body 30 is interposed between two sheets of film-shapedexterior packaging members 40, and then outer edge portions of theexterior packaging members 40 are bonded to each other through thermalfusion and the like, thereby sealing the wound electrode body 30. Atthis time, the adhesive film 41 is interposed between the positiveelectrode lead 31 and the negative electrode lead 32, and each of theexterior packaging members 40. According to this, the nonaqueouselectrolyte battery illustrated in FIGS. 1 and 2 is obtained. Inaddition, instead of the wound electrode body 30, an electrode bodyobtained through lamination of strip-shaped electrode plates and thelike is also possible.

(Second Manufacturing Method)

In the second manufacturing method, first, the positive electrode lead31 is attached to the positive electrode 33, and the negative electrodelead 32 is attached to the negative electrode 34. Then, the positiveelectrode 33 and the negative electrode 34 are laminated on each otherthrough the separator 35 in which a polymer compound is applied to bothsurfaces thereof, and are wound. Then, the protective tape 37 is bondedto the outermost peripheral portion of the resultant wound body toprepare a wound body that is a precursor of the wound electrode body 30.

Then, the wound body is interposed between the two sheets of film-shapedexterior packaging members 40. Outer peripheral portions excluding anouter peripheral portion of one side are bonded through thermal fusionand the like, and then the wound body is accommodated inside theexterior packaging member 40 having a bag shape.

Examples of the polymer compound that is applied to the separator 35include a polymer including vinylidene fluoride as a component, that is,a homopolymer, a copolymer, a multi-component copolymer, and the like.Specifically, polyvinylidene fluoride, a binary copolymer includingvinylidene fluoride and hexafluoropropylene as a component, a ternarycopolymer including vinylidene fluoride, hexafluoropropylene, andchlorotrifluoroethylene as a component, and the like are suitable. Inaddition, the polymer compound may include one or more kinds of otherpolymer compounds in combination with the polymer including vinylidenefluoride as a component.

For example, the polymer compound on the separator 35 may form a porouspolymer compound as described below. That is, first, a solution, whichis obtained by dissolving the polymer compound in a first solventcomposed of a polar organic solvent such as N-methyl-2-pyrrolidone,γ-butyrolactone, N,N-dimethylacetamide, and N,N-dimethyl sulfoxide, isprepared, and the solution is applied to the separator 35. Next, theseparator 35 to which the solution is applied is immersed in a secondsolvent such as water, ethyl alcohol, and propyl alcohol which arecompatible with the polar organic solvent and are a poor solvent for thepolymer compound. At this time, solvent exchange occurs, and a phaseseparation accompanied with spinodal decomposition occurs, whereby thepolymer compound forms a porous structure. Then, the polymer compound isdried to obtain a porous polymer compound having a porous structure.

Then, an electrolyte solution is prepared, and is injected into theinside of the bag-shaped exterior packaging member 40, and then anopening of the exterior packaging member 40 is sealed through thermalfusion and the like. Finally, the exterior packaging member 40 is heatedwhile being weighted so as to bring the separator 35 into close contactwith the positive electrode 33 and the negative electrode 34 through thepolymer compound. According to this, the polymer compound is impregnatedwith the electrolyte solution, the polymer compound gelates, and thus agel-like electrolyte 36 is formed. According to this, the nonaqueouselectrolyte battery illustrated in FIGS. 1 and 2 is obtained. Inaddition, instead of the wound electrode body 30, an electrode bodyobtained through lamination of strip-shaped electrode plates and thelike is also possible.

(Third Manufacturing Method)

In the third manufacturing method, first, the positive electrode lead 31is attached to the positive electrode 33, and the negative electrodelead 32 is attached to the negative electrode 34. Then, the positiveelectrode 33 and the negative electrode 34 are laminated through theseparator 35 and are wound. Then, the protective tape 37 is bonded tothe outermost peripheral portion of the resultant wound body to preparea wound body that is a precursor of the wound electrode body 30.

Then, the wound body is interposed between the two sheets of film-shapedexterior packaging members 40. Outer peripheral portions excluding anouter peripheral portion of one side are bonded through thermal fusionand the like, and then the wound body is accommodated inside theexterior packaging member 40 having a bag shape. Then, a composition foran electrolyte, which includes an electrolyte solution, a monomer thatis a raw material of the polymer compound, a polymerization initiator,and other materials such as a polymerization inhibitor (as necessary),is prepared. The composition for an electrolyte is injected to theinside of the bag-shaped exterior packaging member 40, and then anopening of the exterior packaging member 40 is sealed through thermalfusion and the like. Finally, the monomer is thermally polymerized toform a polymer compound, thereby forming the gel-like electrolyte 36.According to this, the nonaqueous electrolyte battery illustrated inFIGS. 1 and 2 is obtained. In addition, instead of the wound electrodebody 30, an electrode body obtained through lamination of strip-shapedelectrode plates and the like is also possible.

The nonaqueous electrolyte battery according to the first embodiment ofthe present disclosure may be designed in such a manner that anopen-circuit voltage (that is, a battery voltage) in a fully chargedstate per a pair of the positive electrode and the negative electrode isequal to or greater than 4.20 V, 4.25 V, or 4.35 V, and equal to or lessthan 4.65 V, 4.80 V, or 6.00 V. When the battery voltage is made to behigh, it is possible to further increase an energy density. Even in acase where the battery voltage is made to be high, in the embodiment ofthe present disclosure, since the separator having a predeterminedstructure is used, it is possible to suppress deterioration in cyclecharacteristics. For example, in a case where the open-circuit voltageduring full charging is 4.25 V or greater, an amount of lithiumdeintercalated per unit mass increases even in the same positiveelectrode active material in comparison to a battery in which theopen-circuit voltage is 4.20 V. According to this, an amount of thepositive electrode active material and an amount of the negativeelectrode active material are adjusted. As a result, it is possible toobtain a high energy density.

2. Second Embodiment

In a second embodiment, description will be given to an example of abattery pack of a laminate film-type battery (nonaqueous electrolytebattery) provided with the same gel electrolyte layer as in the firstembodiment.

The battery pack is a simple battery pack (also referred to as a softpack). The simple battery pack is embedded in an electronic apparatussuch as a smart phone. In the simple battery pack, a battery cell, aprotective circuit, and the like are fixed with an insulating tape orthe like, a part of the battery cell is exposed, and an output such as aconnector to be connected to a main body of the electronic apparatus isprovided.

An example of a configuration of the simple battery pack will bedescribed. FIG. 4 is an exploded perspective view illustrating aconfiguration example of the simple battery pack. FIG. 5A is a schematicperspective view illustrating external appearance of the simple batterypack, and FIG. 5B is a schematic perspective view illustrating externalappearance of the simple battery pack.

As illustrated in FIG. 4, FIG. 5A, and FIG. 5B, the simple battery packincludes a battery cell 101, electrode leads 102 a and 102 b which areled out from the battery cell 101, insulating tapes 103 a to 103 c, aninsulating plate 104, a circuit substrate 105 in which a protectivecircuit (protection circuit module (PCM)) is formed, and a connector106. For example, the battery cell 101 is the same as the nonaqueouselectrolyte battery according to the first embodiment.

The insulating plate 104 and the circuit substrate 105 are disposed at aterrace portion 101 a that is located at the front end of the batterycell 101, and the lead 102 a and the lead 102 b which are led from thebattery cell 101 is connected to the circuit substrate 105.

The connector 106 for an output is connected to the circuit substrate105. Members such as the battery cell 101, the insulating plate 104, andthe circuit substrate 105 are fixed by bonding the insulating tapes 103a to 103 c to predetermined sites.

3. Third Embodiment Example of Battery Pack

FIG. 6 is a block diagram illustrating an example of a circuitconfiguration in a case of applying the battery (hereinafter,appropriately referred to as a “secondary battery”) according to thefirst embodiment of the present disclosure to a battery pack. Thebattery pack includes an assembled battery 301, an exterior casing, aswitch unit 304 including a charging control switch 302 a and adischarging control switch 303 a, a current detecting resistor 307, atemperature detecting element 308, and a control unit 310.

In addition, the battery pack includes a positive electrode terminal 321and a negative electrode terminal 322. During charging, the positiveelectrode terminal 321 and the negative electrode terminal 322 areconnected to a positive electrode terminal and a negative electrodeterminal of a charger, respectively, to perform charging. In addition,during using of an electronic apparatus, the positive electrode terminal321 and the negative electrode terminal 322 are connected to a positiveelectrode terminal and a negative electrode terminal of the electronicapparatus, respectively, to perform discharging.

The assembled battery 301 is constructed by connecting a plurality ofsecondary batteries 301 a in series and/or in parallel. Each of thesecondary batteries 301 a is the secondary battery of the presentdisclosure. FIG. 6 illustrates a case where six secondary batteries 301a are connected in a type of 2-parallel and 3-series (2P3S) as anexample. However, as is the case with n-parallel and m-series (n and mare integers), any connection method is also possible.

The switch unit 304 includes the charging control switch 302 a, a diode302 b, the discharging control switch 303 a, and a diode 303 b, and iscontrolled by the control unit 310. The diode 302 b is has a reversepolarity with respect to a charging current that flows in a directionfrom the positive electrode terminal 321 to the assembled battery 301,and has a forward polarity with respect to a discharging current thatflows in a direction from the negative electrode terminal 322 to theassembled battery 301. The diode 303 b has a forward polarity withrespect to the charging current and a reverse polarity with respect tothe discharging current. In this example, the switch unit 304 isprovided on a positive side, but may be provided on a negative side.

The charging control switch 302 a is controlled by a charging anddischarging control unit in such a manner that when a battery voltagereaches an over-charging detection voltage, the charging control switch302 a is turned off in order for a charging current not to flow througha current path of the assembled battery 301. After the charging controlswitch 302 a is turned off, only discharging is possible through thediode 302 b. In addition, the charging control switch 302 a iscontrolled by the control unit 310 in such a manner that when a largecurrent flows during charging, the charging control switch 302 a isturned off so as to block a charging current flowing through the currentpath of assembled battery 301.

The discharging control switch 303 a is controlled by the control unit310 in such a manner that when the battery voltage reaches anover-discharging detection voltage, the discharging control switch 303 ais turned off in order for a discharging current not to flow through thecurrent path of the assembled battery 301. After the discharging controlswitch 303 a is turned off, only charging is possible through the diode303 b. In addition, the discharging control switch 303 a is controlledby the control unit 310 in such a manner that when a large current flowsduring discharging, the discharging control switch 303 a is turned offso as to block the discharging current flowing through the current pathof the assembled battery 301.

For example, the temperature detecting element 308 is a thermistor, isprovided in the vicinity of the assembled battery 301, measures atemperature of the assembled battery 301, and supplies a measuredtemperature to the control unit 310. The voltage detecting unit 311measures the voltage of the assembled battery 301 and each of thesecondary batteries 301 a which constitutes the assembled battery 301,A/D converts the measured voltage, and supplies the converted voltage tothe control unit 310. The current measuring unit 313 measures a currentby using the current detecting resistor 307, and supplies the measuredcurrent to the control unit 310.

The switch control unit 314 controls the charging control switch 302 aand the discharging control switch 303 a of the switch unit 304 on thebasis of the voltage and the current which are input from the voltagedetecting unit 311 and the current measuring unit 313, respectively.When any voltage of the secondary batteries 301 a is equal to or lowerthan the over-charging detection voltage or the over-dischargingdetection voltage, or when a large current flows in a drastic manner,the switch control unit 314 transmits a control signal to the switchunit 304 to prevent over-charging, over-discharging, and over-currentcharging and discharging.

Here, for example, in a case where the secondary battery is a lithiumion secondary battery, the over-charging detection voltage is set to,for example, 4.20 V±0.05 V, and the over-discharging detection voltageis set to, for example, 2.4 V±0.1 V.

As the charging and discharging switch, for example, a semiconductorswitch such as MOSFET can be used. In this case, a parasitic diode ofthe MOSFET functions as the diodes 302 b and 303 b. In a case where aP-channel type FET is used as the charging and discharging switch, theswitch control unit 314 supplies control signals DO and CO to gates ofthe charging control switch 302 a and the discharging control switch 303a, respectively. In the case of the P-channel type, the charging controlswitch 302 a and the discharging control switch 303 a are turned on by agate potential that is lower than a source potential by a predeterminedvalue. That is, in a typical charging and discharging operation, thecontrol signals CO and DO are set to a low level, and the chargingcontrol switch 302 a and the discharging control switch 303 a are set toan ON-state.

In addition, for example, during over-charging or over-discharging, thecontrol signals CO and DO are set to a high level, and the chargingcontrol switch 302 a and the discharging control switch 303 a are set toan OFF-state.

A memory 317 is constituted by a RAM or ROM, for example, an erasableprogrammable read only memory (EPROM) that is a nonvolatile memory, andthe like. In the memory 317, a numerical value that is calculated by thecontrol unit 310, an internal resistance value of the battery in aninitial state of each of the secondary batteries 301 a which is measuredat a step of a manufacturing process, and the like are stored inadvance, and appropriate rewriting is also possible. In addition, afull-charging capacity of the secondary battery 301 a is stored in thememory 317, and thus, for example, a residual capacity can be calculatedin combination with the control unit 310.

In the temperature detecting unit 318, a temperature is measured byusing the temperature detecting element 308, and charging anddischarging control is performed during abnormal heat generation orcorrection is performed for calculation of a residual capacity.

4. Fourth Embodiment

For example, the battery according to the first embodiment of thepresent disclosure, and the battery pack according to the secondembodiment and the third embodiment may be used to be mounted on anapparatus such as an electronic apparatus, an electrically drivenvehicle, and an electrical storage device, or for supply of electricpower thereto.

Examples of the electronic apparatus include a notebook computer, aportable digital assistant (PDA), a cellular phone, a cordless phonehandset, a video movie, a digital still camera, an electronic book, anelectronic dictionary, a music player, a radio, a headphone, a gamingmachine, a navigation system, a memory card, a pacemaker, a hearing aid,an electric tool, an electric shaver, a refrigerator, an airconditioner, a television, a stereo, a water heater, a microwave oven, adishwasher, a washing machine, a dryer, an illumination apparatus, atoy, a medical apparatus, a robot, a road conditioner, a signalapparatus, and the like.

In addition, examples of the electrically driven vehicle include arailway vehicle, a golf cart, an electrically driven cart, an electricvehicle (including a hybrid car), and the like, and the batteries areused as a driving power supply or an auxiliary power supply of thevehicles.

Examples of the electrical storage device include power supplies forelectrical storage of buildings starting from a house, a powergenerating facility, and the like.

Hereinafter, among the above-described application examples, specificexamples of the electrical storage system using an electrical storagedevice to which the batteries of the present disclosure are applied willbe described.

As the electrical storage system, for example, the followingconfiguration may be exemplified. A first electrical storage system isan electrical storage system in which an electrical storage device ischarged by a power generating device that performs power generation fromrenewable energy. A second electrical storage system is an electricalstorage system that is provided with an electrical storage device andsupplies electric power to an electronic apparatus that is connected tothe electrical storage device. A third electrical storage system is anelectronic apparatus to which electric power is supplied from anelectrical storage device. This electrical storage system is executed asa system that realizes efficient power supply in cooperation with anexternal power supply network.

In addition, a fourth electrical storage system is an electricallydriven vehicle provided with a conversion device to which electric poweris supplied from an electrical storage device and which converts theelectric power to a driving force of a vehicle, and a control devicethat performs information processing relating to vehicle control on thebasis of information relating to the electrical storage device. A fifthelectrical storage system is a power system which is provided with anpower information transmitting and receiving unit that transmits andreceives a signal to and from other apparatuses through a network, andperforms charging and discharging control of the above-describedelectrical storage device on the basis of the information that isreceived by the transmitting and receiving unit. A sixth electricalstorage system is a power system to which electric power is suppliedfrom the above-described electrical storage device or which supplieselectric power from a power generating device or a power network to theelectrical storage device. Hereinafter, the electrical storage systemwill be described.

(4-1) Electrical Storage System in House as Application Example

An example in which an electrical storage device using the battery ofthe present disclosure is applied to an electrical storage system for ahouse will be described with reference to FIG. 7. For example, in anelectrical storage system 400 for a house 401, electric power issupplied to an electrical storage device 403 from a centralized powersystem 402 such as a thermal power generation 402 a, a nuclear powergeneration 402 b, a hydraulic power generation 402 c through a powernetwork 409, an information network 412, a smart meter 407, a power hub408, and the like. In addition, electric power from an independent powersupply such as an in-house power generating device 404 is supplied tothe electrical storage device 403. The electric power supplied to theelectrical storage device 403 is stored. Electric power that is used inthe house 401 is supplied by using the electrical storage device 403.The same electrical storage system may also be used with respect to abuilding without limitation to the house 401.

The power generating device 404, power consuming devices 405, theelectrical storage device 403, a control device 410 that controlsrespective devices, the smart meter 407, and sensors 411 that acquirevarious pieces of information are provided to the house 401. Therespective devices are connected to each other by the power network 409and the information network 412. As the power generating device 404, asolar cell, a fuel cell, or the like is used, and generated power issupplied to the power consuming devices 405 and/or the electricalstorage device 403. Examples of the power consuming devices 405 includea refrigerator 405 a, an air conditioner 405 b, a television 405 c, abath 405 d, and the like. In addition, examples of the power consumingdevices 405 include an electrically driven vehicle 406. Examples of theelectrically driven vehicle 406 include an electric vehicle 406 a, ahybrid car 406 b, and an electric bike 406 c.

The battery of the present disclosure is applied with respect to thiselectrical storage device 403. For example, the battery of the presentdisclosure may be configured by the above-described lithium ionsecondary battery. The smart meter 407 has a function of measuring theamount of commercial power used and of transmitting the amount that ismeasured to a power company. The power network 409 may be any one of aDC power supply type, an AC power supply type, and non-contact powersupply type, or a combination thereof.

Examples of the various sensors 411 include a motion sensing sensor, aluminance sensor, an object sensing sensor, a power-consumption sensor,a vibration sensor, a contact sensor, a temperature sensor, an infraredsensor, and the like. Information acquired by the various sensors 411 istransmitted to the control device 410. Weather conditions, conditions ofhuman, or the like is grasped by the information transmitted from thesensors 411, and the power consuming devices 405 are automaticallycontrolled. Therefore, it is possible to make the energy-consumptionminimal. In addition, the control device 410 may transmit informationrelated to the house 401 to an external power company or the likethrough the Internet.

Processes such as divergence of power lines and DC-AC conversion areperformed by the power hub 408. Examples of a communication method ofthe information network 412 connected to the control device 410 includea method using a communication interface such as a universalasynchronous receiver-transmitter (UART) (transmission and receptioncircuit for asynchronous serial communication), and a method using asensor network compliant to a wireless communication standard such asBluetooth, ZigBee, and Wi-Fi. The Bluetooth method is applied tomultimedia communication and may perform one-to-multi connectioncommunication. The ZigBee uses a physical layer of institute ofelectrical and electronics engineers (IEEE) 802.15.4. IEEE 802.15.4 isthe name of a short-range wireless network standard called a personalarea network (PAN) or wireless (W) PAN.

The control device 410 is connected to an external server 413. Theserver 413 may be managed by any one of the house 401, the powercompany, and a service provider. Examples of information that istransmitted to and received from the server 413 includepower-consumption information, life pattern information, power rates,weather information, disaster information, and information related topower transaction. These kinds of information may be transmitted to andreceived from in-house power consuming devices (for example, atelevision receiver), but may be transmitted to and received fromdevices (for example, cellular phones) positioned at the outside of thehouse. For example, these kinds of information may be displayed onapparatuses such as a television receiver, a cellular phone, a personaldigital assistant (PDA), and the like which have a display function.

The control device 410 that controls each unit includes a centralprocessing unit (CPU), a random access memory (RAM), a read only memory(ROM), and the like, and is accommodated in the electrical storagedevice 403 in this example. The control device 410 is connected to theelectrical storage device 403, the in-house power generating device 404,the power consuming devices 405, the various sensors 411, and the server413 through the information network 412, and has, for example, afunction of adjusting the amount of commercial power used and an amountof power generation. Furthermore, in addition to this function, thecontrol device 410 may have a function of performing power transactionin a power market, and the like.

As described above, generated electric power of the in-house powergenerating device 404 (photovoltaic generation and wind powergeneration) as well as the centralized power system 402 such as thethermal generation 402 a, the nuclear power generation 402 b, and thehydraulic power generation 402 c may be stored in the electrical storagedevice 403. Therefore, even when the generated electric power of thein-house power generating device 404 varies, it is possible to make anamount of power that is transmitted to the outside uniform, or it ispossible to control discharging as much as necessary. For example, amethod of use described below may be considered. Specifically, theelectric power that is obtained from the photovoltaic generation isstored in the electrical storage device 403, and inexpensive midnightpower is also stored in the electrical storage device 403 at night, andthen the electric power that is stored in the electrical storage device403 is discharged to be used in a period of time at which a rate isexpensive in the day time.

In addition, in this example, an example in which the control device 410is accommodated in the electrical storage device 403 has been described,but the control device 410 may be accommodated in the smart meter 407,or may be configured independently. Furthermore, the electrical storagesystem 400 may be used in a plurality of homes as targets in regard toan apartment house, or may be used in a plurality of detached houses astargets.

(4-2) Electrical Storage System in Vehicle as Application Example

An example in which the present disclosure is applied to an electricalstorage system for a vehicle will be described with reference to FIG. 8.FIG. 8 schematically illustrates an example of a configuration of ahybrid car that employs a series hybrid system to which the presentdisclosure is applied. The series hybrid system is a vehicle thattravels with an electric power-driving force converting device by usingelectric power generated by a generator moved by an engine or theelectric power that is temporarily stored in a battery.

In the hybrid vehicle 500, an engine 501, a generator 502, an electricpower-driving force converting device 503, a driving wheel 504 a, adriving wheel 504 b, a wheel 505 a, a wheel 505 b, a battery 508, avehicle control device 509, various sensors 510, and a charging port 511are mounted. The above-described battery of the present disclosure isapplied to the battery 508.

The hybrid vehicle 500 travels using the electric power-driving forceconverting device 503 as a power source. An example of the electricpower-driving force converting device 503 is a motor. The electricpower-driving force converting device 503 operates by electric power ofthe battery 508, and the torque of the electric power-driving forceconverting device 503 is transferred to the driving wheels 504 a and 504b. In addition, the electric power-driving force converting device 503may be applicable to an AC motor or a DC motor by using DC-AC conversionor invert conversion (AC-DC conversion) as necessary. The varioussensors 510 control the engine speed or the opening degree of a throttlevalve (not illustrated) (throttle opening degree) through the vehiclecontrol device 509. Examples of the various sensors 510 include a speedsensor, an acceleration sensor, an engine speed sensor, and the like.

A torque of the engine 501 may be transferred to the generator 502, andelectric power generated by the generator 502 using the torque may bestored in the battery 508.

When the hybrid vehicle 500 is decelerated by a brake mechanism (notillustrated), a resistance force during the deceleration is added to theelectric power-driving force converting device 503 as a torque, andregenerated electric power that is generated by the electricpower-driving force converting device 503 due to the torque is stored inthe battery 508.

When the battery 508 is connected to an external power supply located atthe outside of the hybrid vehicle 500, electric power may be supplied tothe battery 508 from the external power supply by using the chargingport 511 as an input port and the battery 508 may store the electricpower that is supplied.

Although not illustrated, an information processing device that performsinformation processing related to vehicle control on the basis ofinformation related to the secondary battery may be provided. Examplesof the information processing device include an information processingdevice that performs display of a residual amount of the battery on thebasis of information about the residual amount of the battery, and thelike.

In addition, hereinbefore, description has been made with respect to theseries hybrid car that travels with a motor by using electric powergenerated by a generator moved by an engine or the electric power thatis temporarily stored in a battery as an example. However, the presentdisclosure may be effectively applied to a parallel hybrid car that usesboth the output of the engine and the output of the motor as drivingsources, and utilizes three types of traveling using the engine only,traveling using the motor only, and traveling using the engine and motorby appropriately changing these types. In addition, the presentdisclosure may be effectively applied with respect to a so-calledelectrically driven vehicle that travels using driving by a drivingmotor only without using the engine.

EXAMPLES

Hereinafter, the present disclosure will be described in detail withreference to examples. In addition, a configuration of the presentdisclosure is not limited to the following examples.

Example 1-1 Preparation of Positive Electrode

A positive electrode was prepared as follows. 91 parts by mass of apositive electrode active material (LiCo_(0.98)Al_(0.01)Mg_(0.01)O₂), 6parts by mass of graphite as a conductive agent, and 3 parts by mass ofpolyvinylidene fluoride as a binding agent were mixed with each other toprepare a positive electrode mixture. In addition, the positiveelectrode mixture was dispersed in a N-methyl-2-pyrrolidone as a solventto make the positive electrode mixture have a paste shape. Next, thepositive electrode mixture paste that was obtained was uniformly appliedto both surface of strip-shape aluminum foil having a thickness of 12 μmas a positive electrode current collector, and was dried. After drying,compression-molding was performed by using a roller pressing machine toform a positive electrode active material layer. In addition, areadensity adjustment of the positive electrode active material layer wasperformed by adjusting a thickness and a density in thecompression-molding process while performing heating as necessary. InExample 1, the area density of the positive electrode active materiallayer was adjusted to 31.1 mg/cm². In addition, an aluminum lead waswelded to a portion of the positive electrode current collector in whichthe positive electrode active material layer was not formed to form apositive electrode terminal, thereby obtaining the positive electrode.

[Preparation of Negative Electrode]

A negative electrode was prepared as follows. 90 parts by mass ofgraphite as a negative electrode active material, and 10 parts by massof polyvinylidene fluoride as a binding agent were mixed with each otherto prepare a negative electrode mixture. In addition, the negativeelectrode mixture was dispersed in N-methyl-2-pyrrolidone as a solventto make the negative electrode mixture have a paste shape. Next, thenegative electrode mixture paste that was obtained was uniformly appliedto both surfaces of strip-shaped copper foil which becomes a negativeelectrode current collector and has a thickness of 8 μm, and was dried.After drying, compression-molding was performed by using a rollerpressing machine to form a negative electrode active material layer. Inaddition, a nickel lead was welded to a portion of the negativeelectrode current collector in which the negative electrode activematerial layer was not formed to form a negative electrode terminal,thereby obtaining the negative electrode.

[Preparation of Separator]

As a separator, the following polyethylene film was prepared. A rawmaterial resin obtained by mixing 2 parts by mass of ultrahigh molecularweight polyethylene having a weight-average molecular weight (Mw) of2.5×10⁶, and 13 parts by mass of polyethylene having a weight-averagemolecular weight (Mw) of 2.4×10⁵, and liquid paraffin in an amount inaccordance with a desired structure were mixed with each other toprepare a polyethylene composition solution.

Next, 0.125 parts by mass of 2,5-di-t-butyl-p-cresol, and 0.25 parts bymass oftetrakis[(methylene)-3-(3,5-di-t-butyl-4-hydroxylphenyl)-propionate)]methaneas an antioxidant were added to 100 parts by mass of the polyethylenecomposition solution. The mixed solution was put into a stirrer-equippedautoclave and was stirred at 200° C. for 90 minutes, thereby obtaining auniform solution.

The solution was extruded from a T-die by using an extruder having adiameter of 45 mm, and was drawn by using a cooling roll, therebyforming a gel-like sheet.

The sheet that was obtained was set in a biaxial stretching machine, andsimultaneous biaxial stretching was performed at a stretchingtemperature and in a stretching ratio in accordance with a desiredstructure.

The stretched film that was obtained was washed with methylene chlorideto extract and remove the liquid paraffin that remained, and was dried,thereby obtaining a polyethylene film (separator) having a desiredstructure (the film thickness: 7 μm, the surface roughness maximumheight: 2 μm, the porosity before correction: 30%, the correctedporosity: 25.6%, the air permeability: 250 sec/100 cc, the pore size: 24nm, the tortuosity factor: 1.6, and the film resistance: 0.72 μm).

[Formation of Gel Electrolyte Layer]

A gel electrolyte layer was formed on the positive electrode and thenegative electrode as follows.

First, 80 g of dimethyl carbonate (DMC), 40 g of ethylene carbonate(EC), 40 g of propylene carbonate (PC), 9.2 g of LiPF₆, and 0.8 g ofvinylene carbonate (VC) were mixed with each other to prepare a solution(electrolyte solution).

Next, 10 g of a copolymer of polyvinylidene fluoride (PVdF) andhexafluoropropylene (HFP) (copolymerization weight ratio ofPVdF:HFP=97.3) was added to the solution. The resultant mixture wasuniformly dispersed in a homogenizer, and was heated and stirred at 75°C. until the mixture became colorless and transparent, thereby obtainingan electrolyte solution.

Next, the electrolyte solution that was obtained was uniformly appliedto both surfaces of the positive electrode and the negative electrode bya doctor blade method, respectively. Then, the positive electrode andthe negative electrode, to which the electrolyte solution was applied,was left for one minute in a dryer of which an inside temperature wasmaintained at 40° C. for gelation of the electrolyte solution, therebyforming a gel electrolyte layer having a thickness of approximately 8 μmwas formed on the both surfaces of the positive electrode and thenegative electrode, respectively.

[Assembly of Battery]

A battery was assembled as follows. The positive electrode and thenegative electrode which were prepared as described above were used. Thestrip-shaped positive electrode in which the gel electrolyte layer wasformed on both surfaces thereof, and the strip-shaped negative electrodein which the gel electrolyte layer was formed on both surfaces thereofwere laminated through the separator to obtain a laminated body. Thelaminated body was wound in a longitudinal direction thereof to obtain awound electrode body.

Next, the wound electrode body was interposed between moisture-proofingexterior packaging films (laminate films) in which nylon with athickness of 25 μm, aluminum with a thickness of 40 μm, andpolypropylene with a thickness of 30 μm were laminated in this orderfrom the outermost layer, and the outer peripheral portions of theexterior packaging films were thermally fused under decompression forsealing, thereby closing the wound electrode body was closed in theexterior packaging film. In addition, at this time, the positiveelectrode terminal and the negative electrode terminal were insertedinto a sealed portion of the exterior packaging films, and a polyolefinfilm was disposed at a portion at which the exterior packaging films andthe positive electrode terminal and the negative electrode terminal comeinto contact with each other.

Finally, electrode elements were heated in a state of being sealed inthe exterior packaging films. In this manner, thereby obtaining alaminate film type gel electrolyte battery (with a battery size having athickness of 4.4 mm, a width of 65 mm, a height of 71 mm, and a batteryvolume of 2.03×10⁻⁵ L).

Example 1-2 to Example 1-6, and Comparative Example 1-1

A laminate film type gel electrolyte battery was obtained in the samemanner as in Example 1-1 except that a separator having a filmthickness, a surface roughness maximum height, porosity beforecorrection, corrected porosity, air permeability, a pore size, atortuosity factor, and a film resistance in Table 1 was prepared.

Example 2-1 to Example 2-11, and Comparative Example 2-1 to ComparativeExample 2-3

The area density of the positive electrode active material layer wasadjusted to 34.3 mg/cm². A separator having a film thickness, a surfaceroughness maximum height, porosity before correction, correctedporosity, air permeability, a pore size, a tortuosity factor, and a filmresistance in Table 1 was prepared. A laminated film type gelelectrolyte battery was obtained in the same manner as in Example 1-1except for the above-described configuration.

Example 3-1 to Example 3-3, Example 3-5 to Example 3-10, and ComparativeExample 3-1 to Comparative Example 3-3

The area density of the positive electrode active material layer wasadjusted to 36.3 mg/cm². A separator having a film thickness, a surfaceroughness maximum height, porosity before correction, correctedporosity, air permeability, a pore size, a tortuosity factor, and a filmresistance in Table 1 was prepared. A laminated film type gelelectrolyte battery was obtained in the same manner as in Example 1-1except for the above-described configuration.

Example 3-4

The area density of the positive electrode active material layer wasadjusted to 36.3 mg/cm². A separator having a film thickness, a surfaceroughness maximum height, porosity before correction, correctedporosity, air permeability, a pore size, a tortuosity factor, and a filmresistance in Table 1 was prepared.

Next, polyvinylidene fluoride (PVdF) was dissolved inN-methyl-2-pyrrolidone to prepare a solution. The solution was appliedto both surfaces of the separator. Then, the separator was immersed inwater, and was dried. According to this, a porous polymer compoundhaving a porous structure was formed on both surfaces of the separator.

The positive electrode and the negative electrode, which were preparedin the same manner as in the first embodiment, were brought into closecontact with each other through the separator in which the porouspolymer compound was formed on both surfaces thereof. Then, winding wasperformed in a longitudinal direction and a protective tape was bondedto the outermost peripheral portion of the resultant wound body, therebypreparing a wound electrode body.

The wound electrode body was interposed between parts of an exteriorpackaging member, and three sides of the exterior packaging member werethermally fused. In addition, as the exterior packaging member, amoisture-proofing aluminum laminate film having a structure, in which anylon film with a thickness of 25 μm, aluminum foil with a thickness of40 μm, and a polypropylene film with a thickness of 30 μm were laminatedin this order from the outermost layer, was used.

Then, an electrolyte solution was injected to the inside of the exteriorpackaging member, and the remaining one side was thermally fused underdecompression for sealing. In addition, as the electrolyte solution, anelectrolyte solution, which was prepared by mixing 17 g of ethyl methylcarbonate (EMC), 34 g of ethylene carbonate (EC), 34 g of diethylcarbonate (DEC), 14 g of LiPF₆, and 0.8 g of vinylene carbonate (VC),was used. In addition, the electrolyte solution was interposed betweeniron plates and was heated therein so as to make the porous polymercompound swell, thereby obtaining a gel-shaped electrolyte. According tothis, a laminate film type gel electrolyte battery having the same sizeas in Example 1-1 was obtained.

Example 4-1 to Example 4-4, Example 4-7, and Comparative Example 4-1

The area density of the positive electrode active material layer wasadjusted to 38.5 mg/cm². A separator having a film thickness, a surfaceroughness maximum height, porosity before correction, correctedporosity, air permeability, a pore size, a tortuosity factor, and a filmresistance in Table 1 was prepared. A laminated film type gelelectrolyte battery was obtained in the same manner as in Example 1-1except for the above-described configuration.

Example 4-5 to Example 4-6, and Comparative Example 4-2

The area density of the positive electrode active material layer wasadjusted to 38.5 mg/cm². A separator having a film thickness, a surfaceroughness maximum height, porosity before correction, correctedporosity, air permeability, a pore size, a tortuosity factor, and a filmresistance in Table 1 was prepared. A laminated film type gelelectrolyte battery was obtained in the same manner as in Example 3-4except for the above-described configuration.

Example 5-1 and Comparative Example 5-1

The area density of the positive electrode active material layer wasadjusted to 42.0 mg/cm². A separator having a film thickness, a surfaceroughness maximum height, porosity before correction, correctedporosity, air permeability, a pore size, a tortuosity factor, and a filmresistance in Table 1 was prepared. A laminated film type gelelectrolyte battery was obtained in the same manner as in Example 3-4except for the above-described configuration.

In the above-described Example 1-1 to Example 5-1, and ComparativeExample 1-1 to Comparative Example 5-1, the pore size d (nm) of theseparator, the surface roughness maximum height Rz (μm), the filmthickness L (μm), the porosity ε (%), the air permeability T (sec/100cc), the corrected porosity ε′ (%), the tortuosity factor τ, the areadensity S (mg/cm²) of the positive electrode active material layer, andthe film resistance Ri (μm) were measured as follows.

(Pore Size d)

The pore size d (nm) is an average pore size that was measured by usingnon-mercury Palm Polo meter (product name: IEP-200-A) manufactured bySEIKA Corporation.

(Surface Roughness Maximum Height Rz)

The surface roughness maximum height Rz (μm) was measured in accordancewith JIS B0601 by using a nano-scale hybrid microscope (product name:VN-8000) manufactured by KEYENCE Corporation. The surface roughnessmaximum height is the sum of values obtained by performing measurementwith respect to two main surfaces of the porous film (polyethylene film(separator)), respectively.

(Porosity ε)

The porosity ε (%) of the separator can be measured by using agravimetric method. In the method, 10 sites of the separator are punchedtoward a thickness direction of the separator in a circular shape havinga diameter of 2 cm, and the thickness h of the central portion of thepunched circular film and the mass w of the film are measured,respectively. In addition, a volume V corresponding to 10 sheets offilms and mass W corresponding to 10 sheets of films are obtained byusing the thickness h and the mass w, and the porosity ε (%) can becalculated by the following expression.Porosity ε(%)={(ρV−W)/(ρV)}×100

Here, ρ represents a density of a material of the separator.

(Air Permeability T)

The air permeability T (sec/100 cc) of the separator is Gurleypermeability. The Gurley permeability can be measured in accordance withJIS P8117. The Gurley permeability represents the number of secondstaken for 100 cc of air to pass through a membrane at a pressure of 1.22kPa.

(Film Thickness L)

The film thickness L is an average film thickness that is obtained bymeasuring film thickness of two sheets of the porous films (apolyethylene film (separator)), which are overlapped to each other at aload of 1N, at five sites with a probe of φ5 mm by using a probe typefilm thickness meter (DIGITAL GUAGESTAND DZ-501, manufactured by Sonycorporation), and by calculating the average of measured values/2.

(Corrected Porosity ε′)

The corrected porosity ε′ (%) was calculated from measured values of thefilm thickness, the porosity, the pore size, and the surface roughnessmaximum height by using the following Expression (A).Corrected porosity ε′(%)=[{(L×ε/100)−Rz×0.46/3}/L]×100  Expression (A).

[provided that, L: film thickness (μm), ε: porosity (%), Rz: the surfaceroughness maximum height (the sum of values of a front surface and arear surface) (μm)]

(Tortuosity Factor τ)

The tortuosity factor τ was calculated from measured values of the airpermeability, the corrected porosity, the pore size, and the filmthickness by using the following Expression (B).Tortuosity factor τ={(1.216×ε′Td×10⁻⁴)/L} ^(0.5)  Expression (B)

[provided that, L: film thickness (μm), ε′: corrected porosity (%), T:air permeability (sec/100 cc)]

(Area Density S of Positive Electrode Active Material Layer)

After a battery was completely discharged, the battery was disassembledto take out a positive electrode plate. The positive electrode plate wascleaned with a solvent (DMC: dimethyl carbonate), and was sufficientlydried. A portion (both-surface forming portion) of the positiveelectrode plate, in which the positive electrode active material layerwas formed on both surfaces of the positive electrode current collector,was punched in a predetermined area (punching area) to measure the mass(mg) (referred to as mass A), and then a portion of the positiveelectrode plate, in which a mixture layer was not applied to bothsurfaces, was also punched to measure mass (mg) (referred to as mass B).In addition, the area density was calculated by the followingcalculation formula.Area density(mg/cm²)=(mass A−mass B)÷punching area  Calculation formula:

(Film Resistance Ri)

The film resistance Ri (μm) was calculated from measured values of thecorrected porosity ε′ (%), the film thickness L (μm), and the tortuosityfactor τ by using the following Expression (C).Ri=τ ² L/ε′  Expression (C)

[provided that, L: film thickness (μm), ε′: corrected porosity (%), τ:tortuosity factor]

(Evaluation of Battery: Cycle Test)

The following cycle test was performed with respect to each of thebatteries which were prepared to obtain a capacity retention rate (cycleretention rate). CC-CV charging (constant-current and constant-voltagecharging) was performed for five hours with a current of 0.5 C at apredetermined charging voltage (voltage shown in Table 1) at 23° C., andafter a pause for three hours, discharging was performed with adischarging current of 0.5 C to a voltage of 3.0 V. The operation wasrepeated twice. Second discharging was set as a first cycle, and adischarging capacity at this time was set as an initial dischargingcapacity of the battery. Charging and discharging were repeated underthe same conditions, and [capacity after 500 cycles/initial dischargingcapacity]×100(%) was set as a cycle retention rate. In addition, 1 C isa current value with which a theoretical capacity is discharged (orcharged) in one hour. 0.5 C is a current value with which thetheoretical capacity is discharged (or charged) in two hours.

(Battery Evaluation: Measurement of Volume Energy Density)

The initial discharging capacity (mAh) obtained by the cycle test wasmultiplied by an average discharging voltage (V), and then the resultantvalue was divided by a battery volume, thereby obtaining an energydensity (Wh/L).

Measurement results of Example 1-1 to Example 5-1, and ComparativeExample 1-1 to Comparative Example 5-1 are shown in Table 1.

TABLE 1 Positive electrode Separator Evaluation Area density of Surfaceroughness Porosity Corrected Film Volume positive electrode Film maximumheight before porosity Air resistance energy Cycle retention rate activematerial layer S thickness L Rz correction ε ε′ permeability T Pore sized tortuosity Ri density Voltage Rate The number [mg/cm²] [μm] [μm] [%][%] [sec/100 cc] [nm] factor τ [μm] [Wh/L] [V] [C] of cycles [%] Example1-1 31.1 7 2 30 25.6 250 24 1.6 0.72 374 4.2 0.5 500 90 Example 1-2 72.5 38 32.5 140 27 1.5 0.45 374 4.2 0.5 500 95 Example 1-3 9 2 33 29.6280 21 1.5 0.70 326 4.2 0.5 500 85 Example 1-4 16 1.5 35 33.6 450 18 1.40.98 200 4.2 0.5 500 80 Example 1-5 16 2 38 36.1 500 14 1.4 0.85 200 4.20.5 500 78 Example 1-6 20 2 45 43.5 230 27 1.3 0.74 182 4.2 0.5 500 84Comparative 20 2 30 28.5 510 27 1.5 1.68 180 4.2 0.5 500 69 Example 1-1Example 2-1 34.3 7 2 30 25.6 250 24 1.6 0.72 512 4.3 0.5 500 90 Example2-2 7 2 30 25.6 250 24 1.6 0.72 511 4.3 0.5 500 80 Example 2-3 9 2 3329.6 280 21 1.5 0.70 346 4.2 0.5 500 90 Example 2-4 9 2.5 34 29.7 240 241.5 0.70 332 4.2 0.5 500 90 Example 2-5 9 2 33 29.6 280 21 1.5 0.70 3314.2 0.5 500 80 Example 2-6 5 2 35 28.9 110 31 1.5 0.41 500 4.35 0.5 50095 Example 2-7 9 1.6 45 42.3 80 37 1.3 0.35 397 4.35 0.5 500 93 Example2-8 12 1.4 44 42.2 161 24 1.3 0.47 310 4.2 0.5 500 93 Example 2-9 7 2 3227.6 200 26 1.6 0.62 512 4.35 0.5 500 90 Example 2-10 16 1.5 45 43.6 23521 1.3 0.59 226 4.2 0.5 500 85 Example 2-11 9 2 33 29.6 280 21 1.5 0.70397 4.35 0.5 500 82 Comparative 16 1.5 35 33.6 450 18 1.4 0.98 226 4.20.5 500 60 Example 2-1 Comparative 16 2 38 36.1 500 14 1.4 0.85 226 4.20.5 500 44 Example 2-2 Comparative 20 2 30 28.5 510 27 1.5 1.68 200 4.20.5 500 36 Example 2-3 Example 3-1 36.3 7 2 32 27.6 200 26 1.6 0.62 5484.35 0.5 500 80 Example 3-2 7 2.5 38 32.5 140 27 1.5 0.45 548 4.35 0.5500 90 Example 3-3 9 3.5 35 29.0 210 29 1.5 0.73 445 4.2 0.5 500 80Example 3-4 7 3 35 28.4 230 21 1.5 0.59 481 4.2 0.5 500 84 Example 3-512 1.4 44 42.2 161 24 1.3 0.47 346 4.2 0.5 500 82 Example 3-6 7 2 3025.6 250 24 1.6 0.72 511 4.3 0.5 500 80 Example 3-7 9 2 33 29.6 280 211.5 0.70 410 4.2 0.5 500 73 Example 3-8 16 1.5 45 44.6 235 20 1.3 0.57300 4.2 0.5 500 75 Example 3-9 9 2 33 29.6 280 21 1.5 0.70 407 4.35 0.5500 73 Example 3-10 12 1.5 35 33.1 394 16 1.4 0.75 346 4.2 0.5 500 70Comparative 16 1.5 35 33.6 450 18 1.4 0.98 326 4.2 0.5 500 52 Example3-1 Comparative 16 2 38 36.1 500 14 1.4 0.85 326 4.2 0.5 500 33 Example3-2 Comparative 20 2 30 28.5 510 27 1.5 1.68 250 4.2 0.5 500 28 Example3-3 Example 4-1 38.5 5 2 35 28.9 110 31 1.5 0.41 579 4.35 0.5 500 80Example 4-2 7 2.5 38 32.5 140 27 1.5 0.45 510 4.35 0.5 500 77 Example4-3 9 1.6 45 42.3 80 37 1.3 0.35 457 4.35 0.5 500 80 Example 4-4 12 1.444 42.2 161 24 1.3 0.47 380 4.2 0.5 500 73 Example 4-5 7 3 35 28.4 23021 1.5 0.59 509 4.2 0.5 500 76 Example 4-6 9 3.5 35 29.0 210 29 1.5 0.73445 4.2 0.5 500 70 Example 4-7 9 2 33 29.6 280 21 1.5 0.70 446 4.2 0.5500 70 Comparative 16 1.5 46 44.6 235 20 1.3 0.57 326 4.2 0.5 500 62Example 4-1 Comparative 12 1.5 35 33.1 394 16 1.4 0.75 399 4.2 0.5 50055 Example 4-2 Example 5-1 42.0 7 3 35 28.4 230 21 1.5 0.59 497 4.2 0.5500 73 Comparative 9 3.5 35 29.0 210 29 1.5 0.73 445 4.2 0.5 500 52Example 5-1

In addition, for easy understanding of whether or not Examples andComparative Examples satisfy the following Expressions, FIG. 9 to FIG.13 illustrate L-Ri coordinate planes (L-Ri planes) in a case where thearea density (S) is a predetermined value (31.1 mg/cm², 34.3 mg/cm²,36.3 mg/cm², 38.5 mg/cm², 42 mg/cm²).0.04≦Ri≦−0.07L−0.09×S+4.99Ri=τ ² L/ε′ε′=[{(L×ε/100)−Rz×0.46/3}/L]×100τ={(1.216×ε′Td×10⁻⁴)/L} ^(0.5)  (Expressions)

[provided that, Ri: a film resistance (μm), L: a film thickness (μm), τ:a tortuosity factor, T: air permeability (sec/100 cc), d: a pore size(nm), Rz: a surface roughness maximum height (the sum of values of afront surface and a rear surface) (μm), ε: porosity (%), ε′: correctedporosity (%), and S: the area density of the positive electrode activematerial layer (mg/cm²)]

The measurement values of Examples and Comparative Examples were plottedon the L-Ri coordinate planes of FIG. 9 to FIG. 13. In a case whereplotted points are in ranges of a region S1 to a region S5, it can besaid that the separator (polyethylene film) composed of a porous filmhas a structure satisfying relationships of the above-describedExpressions, and in a case where the plotted points are out of ranges ofthe region S1 to the region S5, it can be said that the separator(polyethylene film) does not have the structure satisfying therelationships of the above-described Expressions.

In addition, the regions S1 to S5, Ri_(min), and Ri_(max) which arerespectively illustrated in FIG. 9 to FIG. 13 are derived in accordancewith the above-described Expressions. Hereinafter, relationalexpressions of the regions S1 to S5, Ri_(min), and Ri_(max) will bedescribed.(Region S1)Ri _(min) ≦Ri≦Ri _(max)  Region S1:Ri _(min)=0.40Ri _(max)=−0.07L−0 09×S+4.99(S=31.1)(Region S2)Ri _(min) ≦Ri≦Ri _(max)  Region S2:Ri _(min)=0.40Ri _(max)=−0.07L−0 09×S+4.99(S=34.3)(Region S3)Ri _(min) ≦Ri≦Ri _(max)  Region S3:Ri _(min)=0.40Ri _(max)=−0.07L−0.09×S+4.99(S=36.3)(Region S4)Ri _(min) ≦Ri≦Ri _(max)  Region S4:Ri _(min)=0.40Ri _(max)=−0.07L−0.09×S+4.99(S=38.5)(Region S5)Ri _(min) ≦Ri≦Ri _(max)  Region S5Ri _(min)=0.40Ri _(max)=−0.07L−0 09×S+4.99(S=42.0)

As illustrated in Table 1, and FIG. 9 to FIG. 13, in Examples 1-1 to 5-1which satisfy the relationships of the above-described Expressions,cycle characteristics were excellent. On the other hand, in ComparativeExamples 1-1 to Comparative Example 5-1 which do not satisfy therelationships of the above-described Expressions, the cyclecharacteristics were not excellent. In addition, a capacity retentionrate in a cycle test which is demanded for an ordinary user isapproximately 70%. Accordingly, during characteristic evaluation, thevalue (70%) was set as a reference value, and in a case where thecapacity retention rate is equal to or greater than the reference value,the cycle characteristics were determined as excellent.

In addition, a preferable film thickness range of the separator has beenexamined as follows from the viewpoint of the energy density of thebattery. Specifically, values of the film thickness L and the volumeenergy density W (Wh/L) of the battery were plotted on a coordinateplane of the horizontal axis x:L (film thickness) and the vertical axisy:log₁₀ (W) for each area density S_(x) of 31.3 (mg/cm²), 34.3 (mg/cm²),36.3 (mg/cm²), 38.5 (mg/cm²), or 42.0 (mg/cm²) in the positive electrodeactive material layer.

In addition, an approximate straight line (primary function: y=ax+b) foreach area density S_(x) was obtained on the basis of the plotting, andthen an intersection (x, y)=(L_(max), log₁₀(300)) between theapproximate straight line and a y value: log₁₀(300) of the volume energydensity W=300 (Wh/L) of the battery was calculated. In addition, thecalculated value of L_(max) represents the maximum film thickness of theseparator which satisfies the volume energy density of 300 Wh/L orgreater in the area density S_(x).

Next, (x, y)=(S_(x), L_(max)) were plotted on the coordinate plane ofthe horizontal axis x:S (area density) and the vertical axis y:L (filmthickness). In addition, an approximate curve (secondary function:y=px²+qx+r) was obtained on the basis of the plotting. The y value inthe area density x=S of the obtained approximate curve(y=−0.0874x²+6.9788x−122.66) represents the maximum film thickness thatsatisfies the volume energy density of 300 Wh/L. Accordingly, in a casewhere the film thickness L of the separator is −0.0873S²+6.9788S−122.66μm or less, the volume energy density of the battery becomes 300 Wh/L orgreater. From these, it could be seen that when the film thickness L ofthe separator is −0.0873S²+6.9788S−122.66 μm or less, the volume energydensity of the battery becomes 300 Wh/L or greater.

4. Other Embodiments

The present disclosure is not limited to the above-described embodimentsof the present disclosure, and various modification or applications canbe made in a range not departing from the gist of the presentdisclosure.

For example, the dimensions, the structures, the shapes, the materials,the raw materials, the manufacturing processes, and the like, which areexemplified in the above-described embodiments and examples, areillustrative only, and different dimensions, structures, shapes,materials, raw materials, manufacturing processes, and the like may beused as necessary.

In addition, the configurations, the methods, the processes, the shapes,the materials, the dimensions, and the like in the above-describedembodiments and examples may be combined with each other as long as thecombination does not depart from the gist of the present disclosure.

The battery according to the above-described embodiments is not limitedto the secondary battery, and may be a primary battery.

In the above-described embodiments and examples, description has beenmade with respect to a battery having a laminate film type batterystructure in which a laminate film is used in an exterior packagingmember, and a battery having a wound structure in which electrodes arewound, but there is no limitation thereto. For example, the presentdisclosure is also applicable to batteries having other structures suchas a cylindrical battery, a stack type battery having a structure inwhich electrodes are stacked, an angular type battery, a coin typebattery, a flat plate type battery, and a button type battery. Examplesof the stack type include a battery structure in which a positiveelectrode and a negative electrode are laminated through each sheet ofseparator, a battery structure in which the positive electrode and thenegative electrode are laminated through a sheet of strip-shapedseparator that is folded in a zigzag folding type, a battery structurein which the positive electrode and the negative electrode are laminatedthrough a pair of separators folded in a zigzag folding type in a statein which the negative electrode is interposed therebetween, and thelike. In addition, for example, the surface layer 35 a that constitutesthe second separator 35 may have a configuration in which particles areomitted.

In addition, as the electrolyte 36, a solid electrolyte and the like maybe used. The electrolyte 36 may contain an ionic liquid (an ordinarytemperature molten salt). The electrolyte 36 may be a liquid electrolytesolution.

The present disclosure may employ the following configurations.

[1] A battery, including:

a positive electrode that includes a positive electrode currentcollector, and a positive electrode active material layer which includesa positive electrode active material and is provided on both surfaces ofthe positive electrode current collector;

a negative electrode;

a separator that includes at least a porous film; and

an electrolyte,

wherein the positive electrode active material includes a positiveelectrode material including a lithium cobalt composite oxide which hasa layered structure and includes at least lithium and cobalt,

an area density S (mg/cm²) of the positive electrode active materiallayer is 27 mg/cm² or greater, and

the porous film satisfies the following Expressions.0.04≦Ri≦−0.07L−0.09×S+4.99Ri=τ ² L/ε′ε′=[{(L×ε/100)−Rz×0.46/3}/L]×100τ={(1.216×ε′Td×10⁻⁴)/L} ^(0.5)  (Expressions)

[provided that, Ri: a film resistance (μm), L: a film thickness (μm), τ:a tortuosity factor, T: air permeability (sec/100 cc), d: a pore size(nm), Rz: a surface roughness maximum height (the sum of values of afront surface and a rear surface) (μm), ε: porosity (%), ε′: correctedporosity (%), and S: the area density of the positive electrode activematerial layer (mg/cm²)]

[2] The battery according to [1],

wherein the electrolyte includes an electrolyte solution and a polymercompound, and the electrolyte is a gel-type electrolyte in which theelectrolyte solution is retained by the polymer compound.

[3] The battery according to [1] or [2],

wherein the electrolyte further includes particles.

[4] The battery according to any one of [1] to [3],

wherein the area density S (mg/cm²) of the positive electrode activematerial layer is 51 mg/cm² or less.

[5] The battery according to any one of [1] to [4],

wherein the thickness of the separator is 3 μm to 17 μm.

[6] The battery according to any one of [1] to [5],

wherein the positive electrode material is a coating particle thatfurther includes a coating layer provided at least on a part of asurface of a particle of the lithium cobalt composite oxide.

[7] The battery according to any one of [1] to [6],

wherein the lithium cobalt composite oxide is at least one kind of alithium cobalt composite oxide expressed by General Formula (Chem. 1).Li_(p)Co_((1-q))M1_(q)O_((2-y))X_(z)  (Chem. 1)

(In Formula, M1 represents at least one kind excluding cobalt (Co) amongelements selected from Group 2 to Group 15, and X represents at leastone kind excluding oxygen (O) among elements in Group 16 and elements inGroup 17. p, q, y, and z are values in ranges of 0.9≦p≦1.1, 0≦q<0.5,−0.10≦y≦0.20, and 0≦z≦0.1.)

[8] The battery according to any one of [1] to [7],

wherein the separator further includes a surface layer which is providedat least on one main surface of the porous film and which includesparticles and a resin.

[9] The battery according to any one of [1] to [8],

wherein the porous film is a polyolefin resin film.

[10] The battery according to any one of [1] to [9],

wherein the thickness of the separator is −0.0873S²+6.9788S−122.66 μm orless.

[11] The battery according to any one of [1] to [10],

wherein the positive electrode, the negative electrode, the separator,and the electrolyte are accommodated in a film-shaped exterior packagingmember.

[12] The battery according to any one of [1] to [11],

wherein an open-circuit voltage in a fully charged state per a pair ofthe positive electrode and the negative electrode is 4.25 V or higher.

[13] A battery pack, including:

the battery according to any one of [1] to [12];

a control unit that controls the battery; and

an exterior packaging member in which the battery is accommodated.

[14] An electronic apparatus, including:

the battery according to any one of [1] to [12],

wherein electric power is supplied from the battery.

[15] An electrically driven vehicle, including:

the battery according to any one of [1] to [12];

a converting device to which electric power is supplied from thebattery, and which converts the electric power to a driving force of avehicle; and

a control device that performs information processing relating tovehicle control on the basis of information relating to the battery.

[16] An electrical storage device, including:

the battery according to any one of [1] to [12],

wherein the electrical storage device supplies electric power to anelectronic apparatus that is connected to the battery.

[17] The electrical storage device according to [16], further including:

a power information control device that transmits and receives a signalto and from other apparatuses through a network,

wherein charging and discharging control of the battery is performed onthe basis of information that is received by the power informationcontrol device.

[18] A power system,

wherein electric power is supplied from the battery according to any oneof [1] to [11], or electric power is supplied to the battery from apower generating device or a power network.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

REFERENCE SIGNS LIST

-   -   30 Wound electrode body    -   31 Positive electrode lead    -   32 Negative electrode lead    -   33 Positive electrode    -   33A Positive electrode current collector    -   33B Positive electrode active material layer    -   34 Negative electrode    -   34A Negative electrode current collector    -   34B Negative electrode active material layer    -   35 Separator    -   35 a Porous film    -   35 b Surface layer    -   36 Electrolyte    -   37 Protective tape    -   40 Exterior packaging member    -   41 Adhesive film    -   101 Battery cell    -   101 a Terrace portion    -   102 a, 102 b Lead    -   103 a to 103 c Insulating tape    -   104 Insulating plate    -   105 Circuit substrate    -   106 Connector    -   301 Assembled battery    -   301 a Secondary battery    -   302 a Charging control switch    -   302 b Diode    -   303 a Discharging control switch    -   303 b Diode    -   304 Switch unit    -   307 Current detecting resistor    -   308 Temperature detecting element    -   310 Control unit    -   311 voltage detecting unit    -   313 Current measuring unit    -   314 Switch control unit    -   317 Memory    -   318 Temperature detecting unit    -   321 Positive electrode terminal    -   322 Negative electrode terminal    -   400 Electrical storage system    -   401 House    -   402 Centralized power system    -   402 a Thermal power generation    -   402 b Nuclear power generation    -   402 c Hydraulic power generation    -   403 Electrical storage device    -   404 Power generating device    -   405 Power consuming device    -   405 a Refrigerator    -   405 b Air conditioner    -   405 c Television    -   405 d Bath    -   406 Electrically driven vehicle    -   406 a Electric vehicle    -   406 b Hybrid car    -   406 c Electric bike    -   407 Smart meter    -   408 Power hub    -   409 Power network    -   410 Control device    -   411 Sensor    -   412 Information network    -   413 Server    -   500 Hybrid vehicle    -   501 Engine    -   502 Generator    -   503 Electric power-driving force converting device    -   504 a Driving wheel    -   504 b Driving wheel    -   505 a Wheel    -   505 b Wheel    -   508 Battery    -   509 Vehicle control device    -   510 Sensor    -   511 Charging port

The invention claimed is:
 1. A battery, comprising: a positive electrodethat includes a positive electrode current collector, and a positiveelectrode active material layer which includes a positive electrodeactive material and is provided on both surfaces of the positiveelectrode current collector; a negative electrode; a separator thatincludes at least a porous film; and an electrolyte, wherein thepositive electrode active material includes a positive electrodematerial including a lithium cobalt composite oxide which has a layeredstructure and includes at least lithium and cobalt, an area density S(mg/cm²) of the positive electrode active material layer is 27 mg/cm² orgreater, and the porous film satisfies the following Expressions:0.04≦Ri≦−0.07L−0.09×S+4.99Ri=τ ² L/ε′ε′=[{(L×ε/100)−Rz×0.46/3}/L]×100τ={(1.216×ε′Td×10⁻⁴)/L} ^(0.5)  (Expressions) [provided that, Ri: a filmleakage resistance (μm), L: a film thickness (μm), τ: a tortuosityfactor, T: air permeability (sec/100 cc), d: a pore size (nm), Rz: asurface roughness maximum height (the sum of values of a front surfaceand a rear surface) (μm), ε: porosity (%), ε′: corrected porosity (%),and S: the area density of the positive electrode active material layer(mg/cm²)].
 2. The battery according to claim 1, wherein the electrolyteincludes an electrolyte solution and a polymer compound, and theelectrolyte is a gel-type electrolyte in which the electrolyte solutionis retained by the polymer compound.
 3. The battery according to claim2, wherein the electrolyte further includes particles.
 4. The batteryaccording to claim 1, wherein the area density S (mg/cm²) of thepositive electrode active material layer is 51 mg/cm² or less.
 5. Thebattery according to claim 1, wherein the thickness of the separator is3 μm to 17 μm.
 6. The battery according to claim 1, wherein the positiveelectrode material is a coating particle that further includes a coatinglayer provided at least on a part of a surface of a particle of thelithium cobalt composite oxide.
 7. The battery according to claim 1,wherein the lithium cobalt composite oxide is at least one kind of alithium cobalt composite oxide expressed by General Formula (Chem. 1):Li_(p)Co_((1-q))M1_(q)O_((2-y))X_(z)  (Chem. 1) (In Formula, M1represents at least one kind excluding cobalt (Co) among elementsselected from Group 2 to Group 15, and X represents at least one kindexcluding oxygen (O) among elements in Group 16 and elements in Group17, and p, q, y, and z are values in ranges of 0.9≦p≦1.1, 0≦q<0.5,−0.10≦y≦0.20, and 0≦z≦0.1).
 8. The battery according to claim 1, whereinthe separator further includes a surface layer which is provided atleast on one main surface of the porous film and which includesparticles and a resin.
 9. The battery according to claim 1, wherein theporous film is a polyolefin resin film.
 10. The battery according toclaim 1, wherein the thickness of the separator is−0.0873S²+6.9788S−122.66 μm or less.
 11. The battery according to claim1, wherein the positive electrode, the negative electrode, theseparator, and the electrolyte are accommodated in a film-shapedexterior packaging member.
 12. The battery according to claim 1, whereinthe open-circuit voltage in a fully charged state per a pair of thepositive electrode and the negative electrode is 4.25 V or higher.
 13. Abattery pack, comprising: the battery according to claim 1; a controlunit that controls the battery; and an exterior packaging member inwhich the battery is accommodated.
 14. An electronic apparatus,comprising: the battery according to claim 1, wherein electric power issupplied from the battery.
 15. An electrically driven vehicle,comprising: the battery according to claim 1; a converting device towhich electric power is supplied from the battery, and which convertsthe electric power to a driving force of a vehicle; and a control devicethat performs information processing relating to vehicle control on thebasis of information relating to the battery.
 16. An electrical storagedevice, comprising: the battery according to claim 1, wherein theelectrical storage device supplies electric power to an electronicapparatus that is connected to the battery.
 17. The electrical storagedevice according to claim 16, further comprising: a power informationcontrol device that transmits and receives a signal to and from otherapparatuses through a network, wherein charging and discharging controlof the battery is performed on the basis of information that is receivedby the power information control device.
 18. A power system, whereinelectric power is supplied from the battery according to claim 1, orelectric power is supplied to the battery from a power generating deviceor a power network.